Exam 1

Question 1

Glycopyrrolate
trade name: robinul-V
anticholinergic

Answer 1

Mechanism of Action: anticholinergic agent/ blocks acetylcholine effect at muscarinic receptor. parasympatholytic. does not cross BBB. produces longer duration of action than atropine.
Uses: inhibit vagal effects and increase HR in animals, decrease secretions.

Question 2

Atropine
anticholinergic

Answer 2

mechanism of action: Anticholinergic agent (blocks acetylcholine effect at muscarinic receptors), parasympatholytic.
As an antimuscarinic agent, it blocks cholinergic stimulation and causes decrease in GI motility and secretions, decrease in respiratory secretions, increased heart rate (antivagal effect), and mydriasis.

use: Atropine is used ordinarily as an adjunct with anesthesia or other procedures. Compared with lower doses, in dogs, 0.06 mg/kg was more effective than 0.02 mg/kg. Atropine may be used during cardiac resuscitation.

Large Animal Dosage
Note that in large animals, atropine has a potent effect on inhibiting GI motility.

Question 3

N-butylscoplammonium bromide (Buscopan)
antispasmodic

Answer 3

mechanism of action: Antispasmodic, antimuscarinic, anticholinergic drug. This is a quaternary ammonium compound derived from belladonna alkaloid.

uses: Butylscopolamine bromide is indicated for treating pain associated with spasmodic colic, flatulent colic, and intestinal impactions in horses.

adverse: As expected with this class of drugs, animals will have increased heart rate, decreased secretions, dry mucous membranes, decreased GI tract motility, and dilated pupils.

Question 4

Activated charcoal

Answer 4

Adsorbent. It binds to other drugs and prevents their absorption from the intestine. It may reduce the absorption of a poison by as much as 75%.

Question 5

Kaolin-pectin
kaopectate
antidiarrheal

Answer 5

The action of kaolin–pectin is believed to be related to the binding of bacterial toxins (endotoxins and enterotoxins) in the gastrointestinal (GI) tract.

Kaolin and pectin combinations are used for the symptomatic treatment of acute diarrhea.

Question 6

Bismuth subsalicylate
pepto-bismol
antidiarrheal

Answer 6

Antidiarrheal agent and GI protectant. Precise mechanism of action is unknown, but antiprostaglandin action of salicylate component may be beneficial for some forms of enteritis.

Bismuth subsalicylate is used for symptomatic treatment of diarrhea in small and large animals.

Question 7

Loperamide
Imodium
analgesic, opioid

Answer 7

Loperamide is an opiate agonist, but its effects are limited to peripheral receptors, particularly those on the GI tract. Like other opiates, loperamide acts on the mu-opiate receptors of the GI tract, where it decreases propulsive intestinal contractions and increases segmentation (an overall constipating effect). It also increases the tone of GI sphincters.

Loperamide is used for symptomatic treatment of acute nonspecific diarrhea. It has been administered orally to dogs and cats. There are no clinical studies in animals, and the use is based on extrapolation from the human uses or anecdotal evidence in animals.

Question 8

Probiotics

Answer 8

another approach in treating diarrhea is the use of probiotics to seed the GI tract with benefi-cial bacteria such as Lactobacillus spp., Enterococcus faecium, and Bifidobacterium . The theory is that there is a delicate balance between normal and patho-genic microorganisms in the GI tract that can be upset by poor husbandry conditions, disease, or stressors (such as transport). Some forms of diarrhea (e.g., secondary to antibiotic drug use) are caused by disruption of the normal bacterial flora of the GI tract. The mechanisms of action of probiotics may involve the nonpathogenic bacteria in probiotic products reducing survival of pathogenic bacteria by competing for nutrients and colonizing sites, producing antimicrobial factors, altering the microenvironment, reducing local inflammation, and alter-ing immune responses. Plain yogurt with active cultures is often used to try to repopulate the GI tract with beneficial bacteria. Trade names of bacterial probiotic products used in vet-erinary medicine include Fastrack® and pectin), ProstoraTM Max, Probiocin®
gel, FortiFlora® , ProviableTM -DC, ProviableTM oral gel for pets, and Probiocin® -KP (with kaolin oral gel for ruminants
(Figure 11-6A). These products may have to be refrigerated to maintain the viability of the bacterial culture.

Question 9

Laxatives: osmotic

Answer 9

Osmotic laxatives produce a hyperosmolar environment in the intestinal lumen that pulls water into the colon and increases water content in the feces, increasing fecal bulk and stimulating peristalsis.

Osmotic (or hyperosmolar) laxatives include salts or saline products, lactulose, and glycerin. Hyperosmolar salts are highly concentrated and pull water into the colon by osmosis, increasing water content in the feces and increasing fecal bulk, which stimulates intestinal stretch receptors to promote peristalsis. T

lactulose: In addition to its osmotic laxative effect, it is also used to prevent and treat hepatic encephalopathy by reducing blood ammonia levels (Figure 11-9A and B).Hepatic encephalopathy can be seen secondary to liver disease in small animals and pet birds and potentially in horses with portosystemic shunts. Lactulose is metabolized by bacteria in the colon to low molecular weight acids that draw water into the lumen of the bowel, causing a laxative effect.
• sodium phosphate with sodium biphosphate: Phosphate enemas are not recommended for use in cats because they can cause life-threatening hyperphosphatemia and hypocalcemia.
• magnesium sulfate (Epsom Salts) • magnesium hydroxide (Carmilax-Powder® • polyethylene glycol (PEG)-electrolyte solution
, Magna

Question 10

Laxatives: irritant

Answer 10

Stimulant (irritant or contact) laxatives increase peristalsis by chemically irritating sensory nerve endings in the intestinal mucosa. Their site of action may vary from affecting only the large or small intestine to affecting the entire GI tract. Although most stimulant laxatives come from nat-ural sources, two agents (bisacodyl and phenolphthalein) are synthetic. These drugs can cause abdominal discomfort. There are no stimulant/irritant laxative drugs approved for use in veter-inary species and little clinical research into their effects. Dosing is extrapolated from human dosing. Examples in this group include the following:
• bisacodyl is a cathartic that comes in enteric-coated and suppository forms. Adverse effects include cramping and diarrhea. Tablets should not be crushed or chewed, as this will result in intense abdominal cramping. Milk or antacids should not be given within one hour of administration of this drug, as they may dissolve the enteric coating.
• castor oil has an active ingredient (ricinoleic acid) that is liberated in the small intestine. Ricinoleic acid inhibits water and electrolyte absorption, leading to fluid accumulation in the GI tract and increased peristalsis. Adverse effects include diarrhea, abdominal pain, and electrolyte imbalance.
• senna is the active ingredient in human products such as Senokot®
and many generic products. It has therapeutic and adverse effects similar to other drugs in this group.

Question 11

Laxatives: bulk forming

Answer 11

The bulk-forming laxatives are natural fibrous substances or semisynthetic compounds added to the diet that absorb water into the intestine, increase fecal bulk, and stimulate peristalsis, result-ing in large, soft stool production. Bulk-forming laxatives are poorly digestible fiber substances obtained mainly from cereal grains, wheat bran, vegetable sources (such as pumpkin), and psyl-lium (a fibrous plant seed). Animals should be well hydrated before starting fiber supplementation to minimize the potential for impaction of fiber in the constipated colon. Bulk-forming laxatives are usually preferred to stimulant/irritant laxatives because they usually produce normally formed stools, are more effective, and they are well tolerated with few adverse effects. Most commercial products contain psyllium, also called plantago seed (the seed coating absorbs water and swells). Most bulk-forming laxatives have minimal effects on nutrient absorption and are not systemically absorbed. Examples include the following:
• psyllium hydrophilic mucilloid (Equine Psyllium®
• calcium polycarbophil
• bran

Question 12

Laxatives: emollient/stool softener

Answer 12

Emollients are stool softeners (which reduce stool surface tension and reduce water absorption through the colon), lubricants (which facilitate passage of fecal material, increasing water reten-tion in stool), and fecal wetting agents (detergent-like drugs that permit easier penetration and mixing of fats and fluid with the fecal mass, resulting in a softer stool that is more easily passed). Emollients enhance lipid absorption and impair water absorption and are not absorbed systemi-cally, and thus have fewer adverse effects than osmotic laxatives. Adverse effects are rare but at high dosages abdominal cramping and diarrhea are possible. Examples include the following:
• docusate sodium, also known as docusate sodium sulfosuccinate (DSS), is available in oral and enema form (Pet-Ema®Docu-SoftTM ).
• docusate calcium is available in regular and soft gel capsules.

Question 13

Laxatives-Lubricant

Answer 13

petroleum in solid form is called white petrolatum, which is the active ingredient in products used to prevent and treat hair balls in cats (CatLax®
, Laxatone® ) (Figure 11-10B and C).Petro-leum in liquid form is called mineral oil, and it is commonly administered via nasogastric tube to horses as a laxative during colic episodes. Proper placement of the nasogastric tube is imperative, as aspiration of petroleum products is likely to be fatal. Oral petroleum can also be used to decrease absorption of fat-soluble toxins. Mineral oil and white petrolatum are lubri-cant laxatives that inhibit water absorption from the colon and make fecal passage easier. Their effects are moderate, and lubricant laxatives are beneficial in mild cases of constipation.

Question 14

Petroleum Vs mineral oil

Answer 14

petroleum is solid form
mineral oil is liquid form of petroleum

Question 15

Enema:Phosphate

Answer 15

Sodium phosphate is a saline laxative that is thought to work by increasing fluid in the small intestine. It usually causes a bowel movement after 1 to 5 minutes.

Mild abdominal discomfort/cramps or gas may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

dont use in cats

Question 16

Enema: DSS ( docusate)

Answer 16

DOCUSATE (doc CUE sayt) prevents and treats occasional constipation. It works by softening the stool, making it easier to have a bowel movement. It belongs to a group of medications called laxatives.

Better/ safer enema

Question 17

Metoclopramide
reglan
antiemetic

Answer 17

Metoclopramide is an antiemetic and prokinetic drug that has been used in small animals for many years to control postoperative vomiting and stimulate GI motility.

Metoclopramide is used primarily for gastroparesis and treatment of vomiting. It is not effective for dogs with gastric dilation and should not be used in dogs with megaesophagus.

Adverse effects are primarily related to blockade of central dopaminergic receptors. Adverse effects similar to those that are reported for other centrally acting D2-receptor antagonists such as phenothiazines.

Do not use in patients with epilepsy or with diseases caused by GI obstruction. Use cautiously in horses because dangerous behavior changes may occur.

Question 18

Emetic: Apomorphine

Answer 18

Emetic drug. Apomorphine is opiate derivative that crosses the blood–brain barrier and stimulates dopamine (D2) or chemoreceptor trigger zone receptors in the vomiting center. It promptly causes vomiting in dogs. Although it is easily absorbed from mucosal surfaces (e.g., conjunctiva of the eye), it is not absorbed orally because of first-pass effects.

Apomorphine is indicated for inducing emesis in animals that have ingested toxic agents. After SQ administration, the onset of effect is 10 minutes or shorter. It is promptly effective for inducing vomiting in dogs but less so in cats.

Question 19

Emetic drug: Xylazine

Alpha2-adrenergic agonist, analgesic, sedative

Answer 19

Xylazine is the oldest alpha2-adrenergic agonists used in veterinary medicine. Alpha2 agonists decrease release of neurotransmitters from the neuron. They decrease transmission via binding to presynaptic alpha2 receptors (negative-feedback receptors).

Xylazine has been used for many years for short-term sedation, anesthesia, and analgesia in horses, dogs, cats, cattle, and exotic animals. Like other alpha2 agonists, it is used as an anesthetic adjunct and analgesic.

In small animals, vomiting is the most common acute effect, which is more prominent in cats than dogs. Xylazine produces sedation and ataxia, which is expected from all alpha2 agonists.

Use with opioid analgesic drugs greatly enhances the central nervous system depression. Consider lowering doses if administered with opioids. Do not administer with other drugs that cause significant cardiac depression.

Question 20

Emetic Drug: Ropinirole
requip XL, Requip

Answer 20

opthalmic clevor
first fda approved emetic for dogs
wear gloves and eyewear
dopamine agonist with selectivity for the dopamine D2 receptor family
where does dopamine act to cause emesis? CRTZ

Question 21

Emetic drugs: hydrogen peroxide

Answer 21

can induce vomiting, can cause gastritis, GI ulceration

Question 22

aluminum and Mg salts

Answer 22

A. Both are locally acting antacids whos goal is to neutralize stomach acid (HCl) and aid in prevention or treatment of ulcers
B. Magnesium hydroxide
a. Greater neutralizing power
b. Can cause diarrhea (also acts as an osmotic laxative)
c. Used to increase rumen pH in ruminants with rumen acidosis
d. Contraindicated in animals with kidney disease due to risk of development of electrolyte imbalances
C. Aluminum hydroxide
a. Has also been used to lower high serum phosphate levels
b. Can cause constipation
D. When used together they provide acid neutralization with minimal GI adverse effects

Question 23

H2 histamine receptor blockers:
cimetidine

Answer 23

Histamine H2-receptor antagonists, also known as H2-blockers, are used to treat duodenal ulcers and prevent their return. They are also used to treat gastric ulcers and for some conditions, such as Zollinger-Ellison disease, in which the stomach produces too much acid.

Question 24

H2 receptor blockers: ranitidine
zantac

Answer 24

Ranitidine
a. More potent and longer duration that cimetidine
b. Stimulates gastric emptying and intestinal motility
c. Dosed BID

Question 25

H2 receptor blockers: famotidine
pepcid

Answer 25

Histamine2 antagonist (H2 blocker). Stimulation of acid secretion in the stomach requires activation of histamine type 2 receptors (H2 receptor), gastrin receptors, and muscarinic receptors.

Famotidine, like other H2-receptor blockers, is used to treat ulcers and gastritis in a variety of animals. Although it is often used for animals with vomiting, there are no efficacy data to indicate that it is effective as an antiemetic.

Give IV injections slowly to cats (over 5 minutes) because rapid IV injections may cause hemolysis.

Administer with food for best absorption. Clinical studies for famotidine have not been performed; therefore, optimal doses for ulcer prevention and healing are not known. Dose recommendations are extrapolated from human use, studies in experimental animals, or from anecdotal experience.

Question 26

H2 histamine receptor blockers: nizatidine
axid
antinuclear agent

Answer 26

Nizatidine is a histamine H2-blocking drug used to suppress stomach acid. Nizatidine blocks histamine stimulation of gastric parietal cells to decrease gastric acid secretion.

Nizatidine, like other H2-receptor blockers, is used to treat gastroesophageal reflux, gastric ulcers, and gastritis.

Question 27

Proton pump inhibitors: omeprazole
prilosec, gastrogard
antiulcer agent

Answer 27

Omeprazole is the most widely used proton pump inhibitor (PPI) in animals. Omeprazole inhibits gastric acid secretion by inhibiting the K+/H+ pump (potassium pump). Omeprazole is more potent and longer acting than the histamine H2 antagonists and is associated with better efficacy.

Omeprazole, like other PPIs, is used for treatment and prevention of GI ulcers and gastroesophageal reflux. It has been used in dogs, cats, and exotic species, but most efficacy data for animals have been produced in horses, in which it has been shown that omeprazole is effective for treating and preventing gastric ulcers.

The only reported adverse effect in dogs has been diarrhea in some cases.

Omeprazole is the most common drug of this class used in animals. Other PPIs include pantoprazole (Protonix), lansoprazole (Prevacid), rabeprazole (Aciphex), and the S-isomer of omeprazole, esomeprazole.

Question 28

Proton pump inhibitors: pantoprazole
antiulcer agent

Answer 28

Pantoprazole is a PPI with action similar to another popular drug in this class, omeprazole. Pantoprazole inhibits gastric acid secretion by inhibiting the K+/H+ pump.

Pantoprazole is used for treatment and prevention of GI ulcers and gastroesophageal reflux. Other PPIs include omeprazole, esomeprazole, lansoprazole (Prevacid), and rabeprazole (AcipHex). All PPIs act via a similar mechanism and are equally effective.

Question 29

Proton pump inhibitors: Iansoprazole

Answer 29

Irreversibly bind with the H+-K+-ATPase enzyme known as the proton pump on the surface of parietal cells of the stomach.
a. Inhibits hydrogen ion transport into the stomach so the cell cannot secrete HCl. (Gastric acid production is decreased)

Question 30

Proton pump Inhibtors: Rabeprazole

Answer 30

Rabeprazole is used to treat duodenal ulcers, gastroesophageal reflux disease (GERD), and Zollinger-Ellison syndrome, a condition where the stomach produces too much acid. It may also be used together with antibiotics (eg, amoxicillin, clarithromycin) to treat ulcers associated with infections caused by the H. pylori bacteria. Rabeprazole is a proton pump inhibitor (PPI) that decreases the amount of acid produced by the stomach.

Question 31

sucralfate
carafate and sulcrate
antiulcer agent

Answer 31

Sucralfate is a gastric mucosa protectant that has both antiulcer effects and some esophageal protectant effects. Sucralfate dissociates in the stomach to form sucrose octasulfate and aluminum hydroxide. Sucrose octasulfate polymerizes to a viscous, sticky substance that creates a protective effect by binding to ulcerated mucosa in the upper GI tract.

Sucralfate is used to prevent and treat gastric ulcers and prevent injury from gastroesophageal reflux.

Because sucralfate is not absorbed, it is virtually free of systemic adverse effects.

Question 32

misoprostol ( the protector)
antiulcer

Answer 32

Misoprostol is a synthetic prostaglandin. It is a synthetic analogue of prostaglandin E1 (PGE1). It is an agonist for the prostaglandin receptors E2, E3, and E4, and produces a cytoprotective effect on the GI mucosa.

Misoprostol is used to decrease the risk of GI ulceration when administered concurrently with NSAIDs. Efficacy has been established for this indication in trials with aspirin but not with other NSAIDs in animals.

Adverse effects are caused by effects of prostaglandins. The most common adverse effects are GI discomfort, vomiting, and diarrhea.

Question 33

anti bloat surfactant: polaxalene

Answer 33

Poloxalene is a non-ionic surfactant that lowers the surface tension of the frothy mass so the bubble film is weakened and can no longer contain the gas. The foam collapses back to the liquid level, unblocking the esophagus so that the animal can orally expel gases.F

Question 34

anti- bloat surfactants: docusate
colace, laxative

Answer 34

Docusate sodium and docusate calcium are stool softeners. They act as surfactants to help increase water penetration into feces. They act to decrease surface tension to allow more water to accumulate in the stool.

Docusate is indicated for medical conditions in which softened feces are desirable, such as after intestinal or anal surgery, to help pass hardened feces, and when administering drugs that slow intestinal transit (e.g., opiates). Docusate is indicated for the treatment of constipation.

Some formulations of docusate calcium and docusate sodium products have contained the stimulant cathartic phenolphthalein, which should be used cautiously in cats.

Question 35

parasympathomimetics:
neostigmine

Answer 35

Neostigmine is a cholinesterase inhibitor (anticholinesterase). This drug inhibits the enzyme that metabolizes acetylcholine into inactive products. Therefore it prolongs the action of acetylcholine at the synapse.

Neostigmine is used as an antidote for anticholinergic intoxication. It is also used as a treatment for myasthenia gravis, treatment (antidote) for neuromuscular blockade, and treatment for ileus. It also has been used as a treatment of urinary retention—such as the retention observed in postoperative patients—by increasing the tone of bladder smooth muscle.

Adverse effects are caused by the cholinergic action resulting from inhibition of cholinesterase. These effects are manifest in the GI tract as diarrhea, increased secretions, and smooth muscle contractions.

Do not use with other cholinergic drugs. Anticholinergic drugs (atropine and glycopyrrolate) block the effects.

Question 36

parasympathomimetics:
dexpanthenol aka D-panthenol

Answer 36

Dexpanthenol
a. This is a cholinergic drug that stimulates the parasympathetic system (because it is a precursor to acetylcholine)

Question 37

Domperidone ( dopamine antagonist)
prokinetic agent
trade name: motilium and equidone gel

Answer 37

Domperidone is a benzimidazole with dopamine-2 (DA-2) receptor antagonist activity. It may also have some alpha1 adrenoreceptor antagonist and serotonin 5-HT3 antagonist activity.
Domperidone is a GI motility modifier. domperidone is that the latter does not cross the blood–brain barrier. Therefore, adverse CNS effects are not as much of a problem with domperidone.
Domperidone stimulates the GI motility by inhibiting DA-2 receptors and possibly through increasing acetylcholine effects. The 5-HT3 antagonist activity also may play a role in GI motility.

Domperidone also has endocrine effects by stimulating secretion of prolactin. It is through this action that domperidone is used to stimulate lactation in horses and treat fescue toxicity. In horses, domperidone is used to treat fescue toxicosis and periparturient agalactia in mares. Fescue toxicosis is caused by a fungus that produces a toxin that causes reproductive problems in horses. The action of domperidone to increase lactation is through the stimulation of prolactin.

Acidity is needed for oral administration. Do not administer with stomach antacids, such as omeprazole, cimetidine, or antacids; or acid-suppressing drugs such as omeprazole; or H2 receptor blockers (e.g., famotidine).

Question 38

Pancrelipase
pancreatic enzyme replacement
viokase, pancrezyme, creon, pancreaze, pertzye, zenpep, ultrase

Answer 38

Pancrelipase is a pancreatic enzyme intended to replace natural pancreatic enzymes in animals that have a deficiency. Pancrelipase provides a source of lipase, amylase, and protease.

Pancrelipase provides enzymes lacking for digestion. It should be administered before meals. It is inactivated in gastric acid, and uncoated tablets should be administered with a drug to suppress stomach acid

Oral bleeding has been reported from administration of tablets. The tablets contain potent enzymes, and contact with mucosal membranes may cause lesions and mucosal ulcers.

If antacids are used concurrently, magnesium hydroxide and calcium carbonate may reduce effectiveness

Question 39

Lactulose in addition to being laxative
laxative
chronulac

Answer 39

Lactulose produces a laxative effect by osmotic effect in the colon. It is a nonabsorbed sugar and retains water in the intestine after oral administration via an osmotic effect.

Lactulose is administered orally for treatment of hyperammonemia (hepatic encephalopathy) because it decreases blood ammonia concentrations via lowering the pH of the colon; thus, ammonia in the colon is not as readily absorbed.

Use lactulose with caution in animals with diabetes because it contains lactose and galactose. No drug interactions are reported for animals. It potentially could change the oral absorption of some drugs by changing the intestinal pH.

Question 40

Anthelmintics:Benzimidazoles

Answer 40

benzimidazoles- think azole- albendazole- rounds, flukes, and giardia

Question 41

Anthelmintics: tetrahydropyramidines

Answer 41

Tetrahydropyrimidines are a chemical class Molecular structure of PYRANTELof antiparasitic compounds moderately used on pets, horses and livestock to control parasitic worms. Tetrahydropyrimidines were introduced in the 1960’s. They are used mainly as veterinary anthelmintics

Question 42

Anthelmintics: piperazine
anti parasitic

Answer 42

Piperazine is one of the oldest and still widely used antiparasitic drugs used in animals. Piperazine produces neuromuscular blockade in parasites through selective antagonism of GABA receptors, resulting in opening of chloride channels, hyperpolarization of parasite membrane, and paralysis of worms.

Piperazine is a common antiparasitic drug and is widely available, even over the counter (OTC).

Piperazine is remarkably safe in all species but can cause ataxia, muscle tremors, and changes in behavior.

Question 43

Anthelmintics: emodepside

Answer 43

mainly used for treatment of roundworms.chemical class of depsipeptides.

Question 44

toxicity and uses of orgranophosphates

Answer 44

The clinical signs of organophosphate poisoning occur as a result of excess acetylcholine at nerve endings, which mimics hyperactivity of the parasympathetic nervous system. Signs relative to the alimentary tract include excess salivation, lacrimation, abdominal pain, vomiting, intestinal hypermotility, and diarrhea.

Question 45

anthelmintic means

Answer 45

used to treat infections of animals with parasitic worms

Question 46

benzimidazoles: fenbendazole
panacur
antiparasitic

mechanism of action and spectrum of activity

Answer 46

Fenbendazole is a benzimidazole antiparasitic drug. Like other benzimidazoles, fenbendazole produces a degeneration of the parasite microtubule and irreversibly blocks glucose uptake in parasites. Inhibition of glucose uptake causes depletion of energy stores in the parasite, eventually resulting in death. Mammals are spared from adverse effects because there is no effect on glucose metabolism in mammals.

Fenbendazole is effective for treatment of numerous helminth intestinal parasites in animals, including Toxocara,Toxascaris, Ancylostoma, and Trichuris spp. In dogs, it is effective for most intestinal helminth parasites and against nematodes. In dogs, it also has been used for pulmonary helminths (lungworms), but a longer duration of treatment is needed. Fenbendazole has been effective for treatment of Giardia infection, but higher doses are needed and there may be failure rates as high as 50%. It is effective in cats for treatment of lungworms, flukes, and a variety of helminth parasites. In horses, it is used for the control of large strongyles, small strongyles, pinworms, and ascarids. In pigs, it is effective for lungworms, large roundworms, nodular worms, small stomach worms, and kidney worms. In beef and dairy cattle, it is effective for control of lungworms, stomach worms, barberpole worms, stomach worms, and various intestinal worms.

Question 47

benzimidazoles: febantel
rintal and vercom

mechanism of action and spectrum of activity
antiparasitic

Answer 47

is an antiparasitic that interferes with carbohydrate metabolism in parasitic worms. It suppresses mitochondrial reactions via inhibition of fumarate reductase and interferes with glucose transport. It is metabolized to a benzimidazole compound that binds to structural protein tubulin and prevents polymerization to microtubules, which results in incomplete digestion and absorption of nutrients by the parasite.

is indicated in the control and treatment of larvae and adult stages of intestinal nematodes. In horses, it is used for removal of large strongyles (Strongylus vulgaris, Strongylus edentatus, Strongylus equinus), ascarids (Parascaris equorum, sexually mature and immature), pinworms (Oxyuris equi, adult and fourth-stage larvae), and the various small strongyles.
In dogs and cats, it is used for treatment of hookworms (Ancylostoma caninum and Uncinaria stenocephala), ascarids (Toxocara canis and Toxascaris leonina), and whipworms (Trichuris vulpis). In dogs, it is used in combination with praziquantel for treatment of hookworms (A. caninum and U. stenocephala), whipworms (T. vulpis), ascarids (T. canis and T. leonina), and tapeworms (Dipylidium caninum and Taenia pisiformis).
A formulation of febantel, pyrantel, and praziquantel (Drontal Plus) has been used in cats for treatment of Giardia spp., roundworms, hookworms, and whipworms. In cats, it is also used in combination with praziquantel for removal of hookworms (A. tubaeforme), ascarids (Toxocara cati), and tapeworms (D. caninum and Taenia taeniaeformis).

Question 48

benzimidazoles: albendazole
valbazen
antiparasitic
mechanism of action and spectrum of activity

Answer 48

Benzimidazole antiparasitic drug. Albendazole binds to intracellular beta-tubulin in parasites and prevents the microtubule formation for cell division.

Albendazole is used to treat a variety of intestinal helminth parasites. It has been used for treating parasitic infections of the respiratory tract, including Capillaria aerophila, Paragonimus kellicotti, Aelurostrongylus abstrusus, Filaroides spp., and Oslerus osleri. It is also effective for treatment of Giardia in small animals. However, because albendazole has been associated with bone marrow suppression in dogs and cats, other drugs are preferred in small animals for Giardia.

Question 49

benzimidazoles: oxibendazole

mechanism of action and spectrum of activity
antiparasitic
anthelcide EQ

Answer 49

Oxibendazole is an antiparasitic drug of the benzimidazole class. Like other benzimidazole drugs, it produces a degeneration of the parasite microtubule and irreversibly blocks glucose uptake in parasites. Inhibition of glucose uptake causes depletion of energy stores in parasites, eventually resulting in death. However, there is no effect on glucose metabolism in mammals. It is used to treat intestinal parasites in animals.

Oxibendazole is used in horses for treatment of large strongyles (S. edentatus, S. equinus, and S. vulgaris), small strongyles (species of the genera Cylicostephanus, Cylicocyclus, Cyathostomum, Triodontophorus, Cylicodontophorus, and Gyalocephalus), large roundworms (P. equorum), pinworms (O. equi) including various larval stages, and threadworms (Strongyloides westeri).
Formulations for dogs have contained both diethylcarbamazine citrate and oxibendazole for prevention of Dirofilaria immitis (heartworm disease) and Ancylostoma caninum (hookworm infection) and for treatment of Trichuris vulpis (whipworm infection) and intestinal Toxocara canis (Ascarid infection). However, diethylcarbamazine is no longer used for heartworm disease prevention in dogs because other alternate drugs are available.

Question 50

benzimidazoles: thiabendazole
mechanism of action and spectrum of activity
omnizole, equizole, TBZ
antiparasitic

Answer 50

Thiabendazole is a benzimidazole antiparasitic drug. Like other benzimidazoles, it produces a degeneration of the parasite microtubule and irreversibly blocks glucose uptake in parasites. Inhibition of glucose uptake causes depletion of energy stores in the parasite, eventually resulting in death. However, there is no effect on glucose metabolism in mammals.

Availability of commercial forms of thiabendazole has been limited. Some forms are no longer available. In horses, it has been used for control of large and small strongyles; Strongyloides; and pinworms of the genera Strongylus, Cyathostomum, and Cylicobrachytus and related genera Craterostomum, Oesophagodontus, Poteriostomum, and Oxyuris. In ruminants, it has been used for infections of GI roundworms in sheep and goats (Trichostrongylus spp. Haemonchus spp., Ostertagia spp., Cooperia spp., Nematodirus spp., Bunostomom spp., Strongyloides spp., Chabertia spp., Oesophagostomum spp., Trichostrongylus colubriformis, Trichostrongylus axei, and Ostertagia spp.).

Question 51

relationship between febantel and fenbendazole

Answer 51

febantel is metabolized into fenbendazole after it hits the liver

Question 52

tetrahydropyrimidines: pyrantel
Mechanism of action, spectrum of activity, safety profile
nemex, strongid, priex, pyran
antiparasitic

Answer 52

Pyrantel is one of the oldest antiparasitic drugs but is still used in animal for common intestinal parasites. Pyrantel is in the class of tetrahydropyrimidines. Others in this class include morantel. Pyrantel acts to interfere with ganglionic neurotransmission via blocking with acetylcholine receptors and other sites. This causes paralysis of the parasites. Paralyzed worms are expelled from the intestinal lumen by peristalsis. Pyrantel is poorly water soluble and not absorbed systemically in ruminants, although some absorption occurs in monogastric animals. Most of the activity is confined to the intestinal lumen.

Pyrantel is indicated for treatment of intestinal nematodes. In horses, it is used for treatment and prevention of nematodes, including pinworms (Oxyuris equi), large roundworms (Parascaris equorum), large strongyles (Strongylus edentatus, Strongylus equinus, and Strongylus vulgaris), and small strongyles. When added to medicated feed, it is used to control nematodes, including pinworms (O. equi), large roundworms (P. equorum), large strongyles (S. edentatus, S. vulgaris, and Triodontophorus spp.), and small strongyles. In pigs, it is used for prevention of large roundworm (Ascaris suum) and prevention of the nodular worm Oesophagostomum spp. In dogs and cats, it is used for treatment of nematodes, including hookworms (Ancylostoma spp.) and roundworms (Toxocara cati, Toxocara canis, and Toxascaris leonina). There is some evidence that it is effective for control of some tapeworms, but ordinarily other drugs should be used for tapeworms (see Praziquantel).

Question 53

tetrahydropyrimidines: morantel
Mechanism of action, spectrum of activity, safety profile

Answer 53

The tetrahydropyrimidines include pyrantel pamoate, pyrantel tartrate, and morantel tartrate. These drugs are cholinergic agonists that mimic the action of acetylcholine. This causes initial stimulation and then paralysis of the worm, causing it to release its grip on the intestinal wall and be eliminated in the feces. These drugs come in tablet, paste, suspension (with a somewhat pleasant taste), and top dress forms and adverse effects are rare. They are approved for use in livestock, horses, dogs, and cats. This group is effective at treating ascarids, pinworms, strongyles, and hookworms. Particles in suspensions can settle to the bottom of the container; therefore, sus-pensions should be shaken thoroughly prior to withdrawing a dose.

Question 54

Organophosphates
formulations and toxicity risks

Answer 54

Organophosphates are a group of human-made chemicals that poison insects and mammals. Organophosphates are the most widely used insecticides today. They are used in agriculture, the home, gardens, and veterinary practice.

Question 55

Praziquantel dont worry about drug class name
antiparasitic

Answer 55

Praziquantel is a popular and widely used antiparasitic drug used for many years to eliminate tapeworms in animals. The action on parasites related to neuromuscular toxicity and paralysis via altered permeability to calcium.

Praziquantel is widely used to treat intestinal infections caused by cestodes (tapeworms) (Dipylidium caninum, Taenia pisiformis, and Echinococcus granulosus) and removal and control of canine cestode Echinococcus multilocularis. In cats, it is used for removal of feline cestodes D. caninum and Taenia taeniaeformis. In horses, it is used to treat tapeworms (Anoplocephala perfoliata).
Although there are no products approved for treatment of Spirometra spp. infections in dogs and cats, praziquantel has been used successfully, but a higher dose is needed (25 mg/kg PO) and administered for 2 consecutive days.

Avoid use in cats younger than 6 weeks and dogs younger than 4 weeks. Praziquantel has been safe in pregnancy.

Question 56

epsiprantel: dont worry about drug class name
cestex
antiparasitic

Answer 56

Epsiprantel is an anticestodal agent similar to praziquantel. The action of epsiprantel on parasites is related to neuromuscular toxicity and paralysis via altered permeability to calcium. Susceptible parasites include canine cestodes Dipylidium caninum and Taenia pisiformis and feline cestodes D. caninum and T. taeniaeformis.

Like praziquantel, epsiprantel is used primarily to treat infections caused by tapeworms.

Vomiting occurs at high doses. Anorexia and transient diarrhea have been reported. Epsiprantel is safe in pregnant animals.

Question 57

Emodepside dont worry about drug class name

Answer 57

Depsipeptides
Emodepside is a depsipeptides agent. It is effective against nematodes (ascarids and hookworms) by stimulating presynaptic receptors in the neuromuscular junction causing paralysis and death of the parasite. Emodepside is effective against Toxocara cati, Toxascaris leonine, and Ancyclostoma tubaeforme. It is combined with praziquantel in the combination topical product Profender®
Spot
On. It is not used in kittens less than eight weeks of age. Adverse effects include lethargy, salivation, vomiting, and neurological signs (tremors) and are usually the result of the animal’s licking of the application site. Excessive grooming of the application site may also be seen

Question 58

flukicides: clorsulon

Answer 58

Clorsulon, a benzene sulfonamide, inhibits the trematode’s enzyme systems used in energy production and robs the trematode of its energy. Clorsulon is effective against the adult and immature forms of the liver trematode, Fasciola hepatica, in cattle. Clorsulon is available in combination with ivermectin in multiple injectable products including Ivomec®
Plus and Normectin® Plus
(Figure 15-5B). Adverse effects are not common but include swelling at the injection site. These products have weeks-long withdrawal times, so they are not used in female dairy cattle of breeding age.

Question 59

flukicides: albendazole
valbazen
antiparasitic

Answer 59

Benzimidazole antiparasitic drug. Albendazole binds to intracellular beta-tubulin in parasites and prevents the microtubule formation for cell division.

Albendazole is used to treat a variety of intestinal helminth parasites. It has been used for treating parasitic infections of the respiratory tract, including Capillaria aerophila, Paragonimus kellicotti, Aelurostrongylus abstrusus, Filaroides spp., and Oslerus osleri. It is also effective for treatment of Giardia in small animals. However, because albendazole has been associated with bone marrow suppression in dogs and cats, other drugs are preferred in small animals for Giardia.

Adverse effects include anorexia, lethargy, and bone marrow toxicity. Leukopenia and thrombocytopenia are possible in dogs and cats. Albendazole has an affinity for rapidly dividing cells and may cause toxicity to bone marrow and intestinal epithelium. High doses have been associated with bone marrow toxicity in dogs and cats, and it should be used cautiously in small animals. In other species, at approved doses, there has been a wide margin of safety.

Question 60

flukicides: praziquantel
droncit and drontal combination with febantel
antiparasitic

Answer 60

Praziquantel is a popular and widely used antiparasitic drug used for many years to eliminate tapeworms in animals. The action on parasites related to neuromuscular toxicity and paralysis via altered permeability to calcium.

Praziquantel is widely used to treat intestinal infections caused by cestodes (tapeworms) (Dipylidium caninum, Taenia pisiformis, and Echinococcus granulosus) and removal and control of canine cestode Echinococcus multilocularis. In cats, it is used for removal of feline cestodes D. caninum and Taenia taeniaeformis. In horses, it is used to treat tapeworms (Anoplocephala perfoliata).
Although there are no products approved for treatment of Spirometra spp. infections in dogs and cats, praziquantel has been used successfully, but a higher dose is needed (25 mg/kg PO) and administered for 2 consecutive days. Likewise, although no products are approved to treat Diphyllobothrium spp. in dogs and cats, praziquantel has been used to treat pseudophyllidean tapeworms. A dosage of 25 mg/kg PO for 2 consecutive days is used. A dose of 35 mg/kg once PO also has been used in cats.

Avoid use in cats younger than 6 weeks and dogs younger than 4 weeks. Praziquantel has been safe in pregnancy.

Question 61

Coccidiostats: sulfadimethoxine
albon, bactrovet, generic brands
antibacterial

Answer 61

Sulfadimethoxine is a sulfonamide antibacterial. Sulfonamides compete with PABA for an enzyme that synthesizes dihydrofolic acid in bacteria. It is synergistic with ormetoprim and used in combination in formulations for small animals. Like other sulfonamides, it has a broad spectrum of activity, including gram-positive bacteria, gram-negative bacteria, and some protozoa. However, when used alone, resistance is common.

Indications and Clinical Uses
Sulfadimethoxine is used as a broad-spectrum antimicrobial to treat or prevent infections caused by susceptible organisms, usually in livestock. Infections treated may include pneumonia, intestinal infections (especially coccidia), soft tissue infections, and UTIs. It is also approved for treatment of calf diphtheria and foot rot associated with Fusobacterium necrophorum susceptible to sulfadimethoxine. However, resistance is common unless combined with ormetoprim (see Primor).

Sulfonamides may interact with other drugs, including warfarin, methenamine, dapsone, and etodolac. They may potentiate adverse effects caused by methotrexate and pyrimethamine. Sulfonamides increase the metabolism of cyclosporine, resulting in decreased plasma concentrations. Methenamine is metabolized to formaldehyde, which may form a complex and precipitate with sulfonamides. When sulfonamides are administered to horses that are receiving detomidine, these horses may develop cardiac arrhythmias. This precaution is only listed for IV forms of trimethoprim–sulfonamides.

Usually, sulfonamides such as sulfadimethoxine are rarely used alone in small animals and horses. There is no clinical evidence that one sulfonamide is more or less toxic or efficacious than another sulfonamide. Sulfadimethoxine has been combined with ormetoprim in Primor.

Question 62

Coccidiostats: amrolium competes with protozoa for thiamine

Question 63

coccidiostats
Monensin- an ionophore. dont worry about MOA. Worry about who not to feed it to, and why

Answer 63

horse
ionophore hypersensitivity

Question 64

Ponazuril-Marquis
Specifically targeted to enzyme systems in protozoa (safety profile?) Approved in horses for?
Antiprotozoal

Answer 64

Ponazuril is an antiprotozoal drug used in animals to control infections caused by protozoa. It is also considered a coccidiostat. Ponazuril (also known as toltrazuril sulfone) is a metabolite of the poultry antiprotozoal drug toltrazuril. Ponazuril is a triazine-based drug that acts to inhibit enzyme systems in protozoa or decreasing pyrimidine synthesis. It is specific for apicomplexan organisms because the action attacks the apicoplast organelle in protozoa. This action produces a specific effect as an antiprotozoal agent without affecting other organisms or the treated animal. It is approved for use in horses but also has been used in puppies, kittens, exotic, and zoo animals for treatment of coccidial infections.

Ponazuril is FDA approved for use as a treatment of equine protozoal myeloencephalitis (EPM) caused by S. neurona. In clinical studies in horses with EPM, 62% of 101 horses were treated successfully with dosages of 5 or 10 mg/kg for 28 days. Although successful treatment was reported after 28 days, longer treatment duration may be needed in some animals to resolve the infection and prevent relapse.

Question 65

diclazuril
Specifically targeted to enzyme systems in protozoa (safety profile?) Approved in horses for?

Answer 65

Diclazuril is an antiprotozoan drug used most often as a coccidiostat. Diclazuril is in the class of triazinone antiprotozoals that is effective for treating infections caused by Isospora spp., Toxoplasma gondii, and Eimeria spp. and has been used for treating coccidiosis. It also has been used in horses to treat equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona. Although the exact mechanism of action is currently under investigation, diclazuril exerts its effect on S. neurona effect by inhibiting merozoite production.

Dosage information for diclazuril has been based on approved indications, experimental studies, pharmacokinetic data, and clinical experience. Ponazuril is another related agent used for treating EPM in horses.

Question 66

avernmectins: ivermectin
heartgard, ivomec, eqvalan liquid, equimectrin, privermectin

Answer 66

Ivermectin is an antiparasitic drug of the avermectin class. It is a prototype for this class of antiparasitic agents, which also includes eprinomectin and milbemycins (milbemycin and moxidectin). These drugs are macrocyclic lactones and share many similarities, including mechanism of action. These drugs are neurotoxic to parasites by potentiating glutamate-gated chloride ion channels in parasites. Paralysis and death of the parasite are caused by increased permeability to chloride ions and hyperpolarization of nerve cells.

Ivermectin is used in horses for the treatment and control of large strongyles (adult) (Strongylus vulgaris, Strongylus edentatus, and Triodontophorus spp.), small strongyles (adult and fourth-stage larvae) (Cyathostomum spp., Cylicocyclus spp., Cylicostephanus spp.), pinworms (adult and fourth-stage larvae) (Oxyuris equi), large roundworms (adult) (Parascaris equorum), hairworms (adult) (Trichostrongylus axei), large-mouth stomach worms (adult) (Habronema muscae), neck threadworms (microfilariae) (Onchocerca spp.), and stomach bots (Gastrophilus spp.).

Toxicity may occur at high doses and in breeds in which ivermectin crosses the blood–brain barrier. Sensitive breeds include collies, Australian shepherds, Old English sheepdogs, longhaired whippets, and Shetland sheepdogs. Toxicity is neurotoxic and signs include hypersalivation, depression, ataxia, difficulty with vision, coma, and death. Sensitivity to ivermectin occurs in certain breeds because of a mutation in the multidrug resistance gene (ABCB1, formerly MDR1 gene) that codes for the membrane pump P-glycoprotein.

Do not administer to animals younger than 6 weeks of age. Animals with high numbers of microfilaremia may show adverse reactions to high doses. If dogs are sensitive to ivermectin (see earlier list of breeds), they may be sensitive to other drugs in this class (other avermectins). Ivermectin at approved clinical doses for treatment of endoparasites or heartworm prevention has been safe in pregnant animals. At high doses used for treating demodicosis, safety during pregnancy is not known, but there have been no reports of teratogenic effects.

Except for low doses used for heartworm prevention, do not administer with drugs that could potentially increase the penetration of ivermectin across the blood–brain barrier. Such drugs include ketoconazole, itraconazole, cyclosporine, and calcium-channel blockers.

Ivermectin is used in a wide range of animals for internal and external parasites. Dosage regimens vary, depending on the species and parasite treated. Heartworm prevention is the lowest dose; other parasites require higher doses. Products for heartworm prevention and a topical form are the only forms approved for small animals; for other indications, large-animal injectable products are often administered PO, IM, or SQ to small animals.

Question 67

selamectin
selarid, revolution
antiparasitic

Answer 67

Selamectin is an antiparasitic agent with action similar to ivermectin. It is a microfilaricide for heartworm prevention in dogs and cats. Selamectin is a semisynthetic avermectin. Avermectins (ivermectin-like drugs) and milbemycins (milbemycin, doramectin, and moxidectin) are macrocyclic lactones. Avermectins and milbemycins share similarities, including mechanism of action.

Selamectin is approved for prevention of heartworms; control of fleas, mites, and ticks in dogs; and prevention of heartworms, control of fleas, mites, hookworms, and roundworms in cats. Selamectin also can be used to treat scabies (Sarcoptes spp.) and is sometimes preferred over ivermectin.

Transient, localized alopecia, with or without inflammation, at or near the site of application is observed in approximately 1% of treated cats. Other adverse effects include nausea, lethargy, salivation, tachypnea, and muscle tremors.

Question 68

doramectin
dectomax
antiparasitic

Answer 68

Doramectin is used for treatment or prevention of GI parasite (nematode) infections in livestock, lice infestation, lungworm infection, and treatment of scabies. There are reports of a single injection (200–300 mcg/kg) used in cats for treatment of notoedric mange (infections from the mite Notoedres cati). In dogs, it has been used for treatment of Demodex infection, but there are other agents available that are effective and possibly safer.

Toxicity may occur at high doses and in breeds in which ivermectin-like drugs cross the blood–brain barrier. Sensitive breeds include collies, Australian shepherds, Shetland sheepdogs, Old English sheepdogs, and some related breeds. Toxicity is neurotoxic, and signs include depression, ataxia, impaired vision, coma, and death. Sensitivity to ivermectin-like drugs may be because of mutation in the blood–brain barrier (p-glycoprotein deficiency).

Doramectin is only approved in cattle but there is extralabel use in other animals. Certain breeds of dogs (Shetland sheepdogs and collie-type breeds) are more sensitive to adverse effects than other breeds.

Question 69

eprinomectin
eprinix, longrange, eprizero

Answer 69

Eprinomectin is an antiparasitic drug of the avermectin class. Avermectins (ivermectin-like drugs), such as eprinomectin and milbemycins (milbemycin and moxidectin), are macrocyclic lactones and share similarities, including mechanism of action. These drugs are neurotoxic to parasites by potentiating glutamate-gated chloride ion channels in parasites. Paralysis and death of the parasite are caused by increased permeability to chloride ions and hyperpolarization of nerve cells. These drugs also potentiate other chloride channels, including ones gated by gamma-aminobutyric acid (GABA).

Eprinomectin is indicated for treating cattle with gastrointestinal (GI) nematodes, roundworms, lungworms, cattle grubs (all stages), lice, mange mites, and flies. The duration of the sustained-release injection for GI parasites and lungworms is 100–120 days. The injection formulation can also be administered SQ for the treatment, protection, and control of Bunostomum phlebotomum for 150 days after treatment.

Toxicity may occur at high doses and in canine breeds in which this class of drugs crosses the blood–brain barrier. Toxicity is neurotoxic, and signs include hypersalivation, depression, ataxia, difficulty with vision, coma, and death.

Eprinomectin is approved in cattle for treating GI nematodes, roundworms, lungworms, cattle grubs (all stages), lice, mange mites, and flies. It is approved as a transdermal solution in cats for preventing heartworms and GI parasites in combination with praziquantel.

Question 70

moxidectin

Mechanism of action Why they have a great safety profile in most mammals
proheart, protheart 6
antiparasitic

Answer 70

Moxidectin is an antiparasitic drug in the milbemycin class. Avermectins (ivermectin-like drugs) and milbemycins (milbemycin and moxidectin) are macrocyclic lactones and share similarities, including mechanism of action. Moxidectin is 100 times more lipophilic than ivermectin.

Moxidectin is used in dogs to prevent infection of heartworm (Dirofilaria immitis). In dogs, it can also be used and for the treatment and control of A. caninum, U. stenocephala, T. canis, Toxascaris leonina, and T. vulpis.
Moxidectin also has been used to treat Demodex infections in dogs at high doses. In cats, it is used for the prevention of heartworm disease caused by D. immitis; for the treatment and control of intestinal roundworms (Toxocara cati), and hookworms (Ancylostoma tubaeforme).

In cattle, moxidectin injectable is used to treat intestinal roundworms (Ostertagia ostertagi [adults and inhibited fourth-stage larvae], Haemonchus placei [adults], Trichostrongylus axei [adults], T. colubriformis [fourth-stage larvae], Cooperia oncophora [adults], C. punctata [adults and fourth-stage larvae], C. surnabada [adults and fourth-stage larvae], Oesophagostomum radiatum [adults and fourth-stage larvae], Trichuris spp. [adults]), lungworms (Dictyocaulus viviparus [adults and fourth-stage larvae]), grubs (Hypoderma bovis and H. lineatum), mites (Psoroptes ovis [P. communis var. bovis]), and lice (Linognathus vituli and Solenopotes capillatus).

Toxicity is the result of potentiation of glutamate-gated chloride channels and GABA channels, resulting in hyperpolarization of membranes. Toxicity may occur at high doses and in breeds in which moxidectin crosses the blood–brain barrier.

Do not use the 2.5% topical solution in cats. Do not use in dogs younger than 2 months of age. Despite the safety margin listed in the Adverse Reactions and Side Effects section, caution is advised when administering moxidectin at high doses to ivermectin-sensitive breeds.

Do not administer with drugs that could potentially increase the penetration of ivermectin across the blood–brain barrier. Such drugs include ketoconazole, itraconazole, cyclosporine, and calcium-channel blockers (see Appendix J

Question 71

milbemycin
interceptor, safeheart
Mechanism of action Why they have a great safety profile in most mammals
antiparasitic

Answer 71

Do not administer with drugs that could potentially increase the penetration of ivermectin across the blood–brain barrier. Such drugs include ketoconazole, itraconazole, cyclosporine, and calcium-channel blockers (see Appendix J

Milbemycin is used as a heartworm preventative, miticide, and microfilaricide. It is also used to control infections of hookworm, roundworms, and whipworms. It has been used in combination with flea control drugs (see Sentinel, which contains milbemycin oxime and lufenuron).

At doses of 5 mg/kg, it was well tolerated in most dogs (10 times the heartworm preventative dose). At 10 mg/kg (20 times the heartworm preventative dose), it caused depression, ataxia, and salivation in some dogs. Toxicity may occur at high doses and in breeds in which milbemycin crosses the blood–brain barrier at dosages as low as 1.5 mg/kg per day.

Do not use in dogs that have shown sensitivity to ivermectin or other drugs in this class (see previous breed list). Treatment using three times the daily doses from mating to 1 week before weaning did not produce any adverse effects in the pregnant bitch, the fetus, or puppies.

Do not use with drugs that may increase penetration across the blood–brain barrier. Such drugs include p-glycoprotein inhibitors such as ketoconazole, cyclosporine, quinidine, and some macrolide antibiotics (see Appendix J for a list of p-glycoprotein inhibitors).

Question 72

MDR1 mutation- who is most likely to have it, and what are the implications?

Question 73

Ivermectin with proven safety in MDR1+ dogs?

Answer 73

shetland sheepdogs, australian shepards, collies, collie crosses. Lacotnes easily enter CNS and cause neuro toxicity. resulting in depression , ataxia and possibly death

Question 74

Melarsomine
immiticide
antiparasitic
Adverse effects of drug and of HW disease treatment in Stages 3 and 4

Answer 74

Melarsomine is an organic arsenical compound, primarily for treating heartworm disease in animals. Arsenicals alter glucose uptake and metabolism to eliminate heartworms. Melarsomine has replaced older arsenicals such as thiacetarsamide (Caparsolate) for treating heartworm disease.

Melarsomine is used for heartworm adulticide therapy. See Instructions for Use for proper administration. Melarsomine is highly effective for eliminating heartworms in dogs. Efficacy in cats is only 36% and not recommended. Usually, cats are not treated because it is a self-limiting disease, and only supportive treatment is administered (corticosteroids, bronchodilators, and antiemetics).

Melarsomine administration may lead to pulmonary thromboembolism 7–20 days after therapy, anorexia (13% incidence), injection-site reaction (32% incidence of myositis), or lethargy or depression (15% incidence). It causes elevations of hepatic enzymes. To prevent adverse reactions of adulticide therapy, the American Heartworm Society recommends a three-dose protocol, whereby the first dose is administered after 2 months of a macrocyclic lactone (e.g., ivermectin) and doxycycline.

Use cautiously in animals with high heartworm burden and use the three-dose protocol to reduce lung injury. Melarsomine may be contraindicated in dogs with class 4 (very severe) heartworm disease until the worm burden is reduced.

Question 75

Antitussives: Torbugesic

Answer 75

Antitussives suppress coughing. Antitussives can be centrally acting (working on the cough cen-ters of the brain stem) or locally acting (soothing irritation to the mucosal lining of the pharynx that can initiate coughing). Locally acting antitussives are usually syrups or lozenges and are not used commonly in veterinary practice. Opioid drugs act on the central nervous system (CNS) to suppress cough (their use as narcotic analgesics was described in Chapter 7 [Drugs Affecting the Nervous System]). Care must be taken when opioids are used, as they may cause respiratory depression. They may also decrease intes-tinal motility and cause sedation in some species, though they may cause excitement in horses and cats. Opioids used as antitussives are Drug Enforcement Administration (DEA)-controlled substances; therefore, careful documentation of their use is required. Opioids used as antitus-sives include butorphanol, hydrocodone, and codeine.

Butorphanol (Torbugesic®Torbutrol® ) is a
C-IV-controlled drug that is available as a solution for injection (with differing concentrations per mL) and in oral tablet form (see Figure 1-7B). It is FDA approved for the relief of nonproductive coughing in dogs.

Question 76

Antitussives: Trimeprazine with prednisolone (Temaril-P°)
temaril, panectyl, alimemazine
antiemetic, phenothiazine

Answer 76

Trimeprazine is a phenothiazine derivative that decreases pruritus in dogs, possibly through antihistamine activity. The antihistamine effects have not been confirmed with independent study, but it may act synergistically with corticosteroids. It also produces sedation similar to other phenothiazines.

Trimeprazine is used alone or in combination with corticosteroids for inflammatory and allergic problems. The most common use is for pruritus in dogs in combination with prednisolone (Temaril-P). It also has been used for treating motion sickness and is approved in combination with prednisolone as an antitussive in dogs.

Question 77

bronchodilators: albuterol

porventil, ventolin, torpex
bronchodilator, beta-agonist

Answer 77

Beta2-adrenergic agonist. Albuterol stimulates beta2-receptors to relax bronchial smooth muscle. It may also inhibit release of inflammatory mediators, especially from mast cells. This mechanism of action has been beneficial to relax bronchial smooth muscle to relieve bronchospasm and bronchoconstriction.
Albuterol exists as two chiral isomers. The R-isomer is the active bronchodilator form; the S-isomer is associated with adverse effects. The formulation levalbuterol is a formulation containing only the R-isomer.

Albuterol is indicated in a variety of airway diseases for bronchodilation. Except for equine use, doses are primarily derived from extrapolation of human doses. Efficacy studies for small animal use are not reported. Onset of action is 15–30 minutes, and duration of action may be as long as 8 hours.

Excessive beta-adrenergic stimulation at high doses results in tachycardia and muscle tremors. Arrhythmias are possible with high doses. All beta2-agonists will inhibit uterine contractions at the end of gestation in pregnant animals.

Question 78

bronchodilators: terbutaline
brethine and bricanyl
bronchodilator, beta agonist

Answer 78

Terbutaline is a beta2-adrenergic agonist. It is used primarily as a bronchodilator. Terbutaline stimulates beta2-receptors to relax bronchial smooth muscle. Terbutaline is more beta2 specific than drugs such as isoproterenol, which affect both beta1- and beta2-adrenergic receptors.

Terbutaline, like other beta2-agonists, is indicated in animals with reversible bronchoconstriction, such as cats with bronchial asthma. It also has been used in dogs to relieve bronchoconstriction and in animals with bronchitis and other airwaydiseases. Is has been useful as an injection to rapidly relieve bronchospasm insmall animals associated with inflammatory airway disease or clinical procedures.

Excessive beta-adrenergic stimulation from terbutaline at high doses can produce tachycardia and muscle tremors. Arrhythmias are possible with high doses. All beta2 agonists inhibit uterine contractions at the end of gestation in pregnant animals.

Administer cautiously to animals with cardiac disease, particularly animals that may be susceptible to tachyarrhythmias. Do not use late in gestation unless the intended effect is to delay uterine contractions.

Question 79

bronchodilators: clenbuterol
ventipulmin
bronchodilator, beta agonist

Answer 79

Clenbuterol is a beta2-adrenergic agonist, with more selective activity on beta2 receptors than beta1 receptors (beta2/beta1 ratio = 4.0). It is used primarily as a bronchodilator because it stimulates beta2 receptors to relax bronchial smooth muscle. It may inhibit release of inflammatory mediators, especially from mast cells, decrease mucus production by goblet cells, and increase rate of mucociliary transport in the airways.

Clenbuterol differs from other beta-agonists because it resists O-sulfate ester conjugation, which leads to a longer half-life compared with other agents. It also has better oral absorption (83%) than other beta-agonists in horses. In horses, the plasma half-life is 13 hours, but in urine, it can be detected for 12 days.
In addition to the effects on respiratory smooth muscle, clenbuterol can produce repartitioning effects, which indicates that it will stimulate development of more muscle (anabolic effect) and less fat (lipolytic effect).

Clenbuterol is indicated for treatment of animals with reversible bronchoconstriction such as horses with equine asthma syndrome and recurrent airway obstruction (RAO), formerly called chronic obstructive pulmonary disease. The response for treating RAO can be variable.

Clenbuterol may produce excessive beta-adrenergic stimulation at high doses (tachycardia and tremors). Arrhythmias occur at high doses. Chronic use may have adverse effects on cardiac function in healthy horses. There have been conflicting studies on the effects of clenbuterol on athletic performance of horses. In one study at approved doses, it did not have any adverse effects on equine cardiac or skeletal muscle.

Do not administer to animals intended for food. Veterinarians should be warned that clenbuterol is often abused in humans for the purpose of muscle building and weight loss. Subsequently, high doses in humans may cause cardiac toxicity, such as arrhythmias. Because clenbuterol is a beta-agonist, other adrenergic drugs potentiate the action. In addition, beta-blocking drugs decrease action. Use with caution with any other drug that may stimulate the heart.

Question 80

epinephrine as a bronchodilator
adrenaline and generic brands
adrenergic agonist

Answer 80

The beta2 −adrenergic effects increase bronchodilation and decrease inflammatory mediators in the airways. Epinephrine is a potent adrenergic agonist with a prompt onset and a short duration of action.

Question 81

theophylline
bronchodilator

Answer 81

Theophylline is a methylxanthine bronchodilator. It is a nonselective PDE inhibitor. PDE is the enzyme that converts cyclic adenosine monophosphate (cAMP) to inactive forms, and cAMP accumulates. Therapeutic effects may be caused by cAMP or antagonism of adenosine. There appears to be both anti-inflammatory action and bronchodilating action.

Theophylline is administered for inflammatory airway disease in cats, dogs, and horses. Use in animals has been primarily derived from empirical use, some experimental models, and experience in humans. There are no well-controlled clinical studies or efficacy trials to document clinical effectiveness. It has been used to control clinical signs of reversible airway constriction, such as seen with feline asthma. In dogs, the uses include collapsing trachea, bronchitis, and other airway diseases.

Adverse effects of theophylline include nausea, vomiting, and diarrhea. With high doses, tachycardia, excitement, tremors, and seizures are possible. Cardiovascular and central nervous system (CNS) adverse effects appear to be less frequent in dogs than people. Overdoses can cause hypokalemia.

Use cautiously with other PDE inhibitors such as pentoxifylline, sildenafil (Viagra), and pimobendan. Many drugs inhibit the metabolism of theophylline and potentially increase concentrations.

Question 82

antihistamines H1 blockers

Answer 82

Antihistamines block the effects of histamine, a chemical released from mast cells that combines with H1
receptors on bronchiolar smooth muscle to cause bronchoconstriction. Histamine also works on other body systems such as the heart (increases heart rate), arterioles (causes vasodila-tion), the CNS (sedation), and the inflammatory response. Antihistamines may occasionally be used in the management of respiratory disease; pyrilamine combined with the sympathomimetic drug pseudoephedrine is available in an unapproved product marketed for the treatment of ROA (heaves) in horses. Generic names for antihistamines usually end with -amine (Figure 9-8C) and examples include diphenhydramine and chlorpheniramine. Adverse effects include CNS depression and anticholinergic effects (dry mouth and urinary retention).

Question 83

Tripelennamine

Answer 83

Antihistamine (H1 blocker). Similar to other antihistamines, tripelennamine acts by blocking the histamine type 1 receptor (H1) and suppresses inflammatory reactions caused by histamine. The H1 blockers have been used to control pruritus and skin inflammation in dogs and cats; however, success rates in dogs have not been high.

Question 84

Diphenhydramine
benadryl
antihistamine

Answer 84

Antihistamine (H1 blocker). Similar to other antihistamines, it acts by blocking the H1 receptor (H1) and suppresses inflammatory reactions caused by histamine. Other commonly used antihistamines include clemastine, chlorpheniramine, and hydroxyzine

Diphenhydramine, like other antihistamines, blocks histamine type 1 (H1) receptors to prevent action of histamine. It is used to prevent acute allergic reactions and for pruritus therapy in dogs and cats. However, success rates for treatment of pruritus have not been high. Diphenhydramine has been used to treat acute allergy episodes caused by mast cell release, allergy, insect bites, and so on.

Sedation is the most common side effect. Sedation is the result of inhibition of histamine N-methyltransferase. Sedation may also be attributed to blockade of other CNS receptors such as those for serotonin, acetylcholine, and alpha-receptors. Antimuscarinic effects (atropinelike effects) also are common, including dry mouth and decreased GI secretions.

Antimuscarinic effects (atropinelike effects) are common. Do not use in conditions for which anticholinergic drugs may be contraindicated, such as glaucoma, ileus, or cardiac arrhythmias. Discontinue administration a minimum of 7 days prior to allergen-specific allergy testing in dogs.

There are no specific drug interactions. However, because of anticholinergic (atropinelike) effects, it may counteract drugs that are administered for a parasympathomimetic action (e.g., drugs used to stimulate intestinal motility).

Question 85

Dopram
doxapram hydrochloride
respiram
respiratory stimulant

Answer 85

Doxapram is a respiratory stimulant. It is a potassium-channel blocking drug and is the oldest known agent (available since the 1960s) in this class used for stimulating respiration. The specific action is to inhibit potassium channels (TASK1, TASK3) on carotid body cells (carotid body chemoreceptors). By blocking these potassium channels, respiratory stimulation is produced by increasing sensitivity to CO2. Doxapram is used primarily in emergency during anesthesia or to decrease the respiratory depressant effects of certain drugs (e.g., opiates, barbiturates).

Doxapram may stimulate respiration in dogs, cats, and horses during and after general anesthesia. It has been used to stimulate respiration in newborn animals following dystocia or cesarean section surgery. Adverse effects have not been reported in animals. In people, it has caused panic, anxiety, sweating, seizures, and cardiovascular stimulation. CNS stimulation and excitement are possible with high doses or rapid infusions. Do not use in animals with cardiac or respiratory arrest. Do not use with positive pressure ventilation.

Question 86

Ace inhibitor: enalapril
enacard, vasotec
vasodilator, agiotensin-converting enzyme

Answer 86

Enalapril is an angiotensin-converting enzyme (ACE) inhibitor. Like other ACE inhibitors, it inhibits conversion of angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor and also stimulates sympathetic stimulation, renal hypertension, and synthesis of aldosterone. The ability of aldosterone to cause sodium and water retention contributes to congestion.

Enalapril, like other ACE inhibitors, is used to treat hypertension and congestive heart failure (CHF). Efficacy for treating CHF has been established from clinical trials and can be used with other drugs such as pimobendan, furosemide, digoxin, and spironolactone. If aldosterone breakthrough occurs with administration of ACE inhibitors, spironolactone may be indicated.

Enalapril may cause azotemia in some patients, but this effect is uncommon. Nevertheless, monitor renal parameters in patients receiving ACE inhibitors, especially if they are receiving diuretics. Discontinue ACE inhibitors in pregnant animals; they cross the placenta and have caused fetal malformations and death of the fetus.

Use cautiously with other drugs known to cause hypotension. The use may exacerbate effects of diuretics. Nonsteroidal anti-inflammatory drugs (NSAIDs) may potentially decrease vasodilating effects, but this has not been shown in studies in animals.

Question 87

Ace inhibitors: benazepril
lotensin
vasodilator, ace inhibitor

Answer 87

Angiotensin-converting enzyme (ACE) inhibitor. Inhibits conversion of angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor and also produces sympathetic stimulation, renal hypertension, and synthesis of aldosterone. The inhibition of aldosterone decreases sodium and water retention. Benazepril, like other ACE inhibitors, produces vasodilation and decreases aldosterone-induced congestion.

Benazepril, like other ACE inhibitors, is used to treat hypertension and congestive heart failure (CHF). Evidence shows that it may decrease the likelihood of developing cardiomyopathy in some dogs, but other studies failed to show this benefit. For treatment of occult mitral valve disease in dogs, there has not been a benefit of therapy.

Benazepril has been well tolerated in dogs and cats with chronic renal failure. However, it may cause azotemia in some patients; carefully monitor renal parameters after initiation of treatment, particularly in patients receiving high doses of diuretics. Monitor patients carefully to avoid hypotension. With all ACE inhibitors, monitor electrolytes and renal function 3–7 days after initiating therapy and periodically thereafter.

Question 88

spironolactone
aldactone and prilactone
diuretic

Answer 88

Spironolactone is considered a potassium-sparing diuretic, but it also acts as an aldosterone antagonist. The action of spironolactone is to interfere with sodium reabsorption in distal renal tubules by competitively inhibiting the action of aldosterone. Aldosterone mediates retention of water and sodium. Spironolactone binds directly to the aldosterone receptor, but at usual doses, it does not block the action of other steroid receptors.

Spironolactone is used for treating high blood pressure and congestion caused by heart failure. It is approved in Europe (Prilactone) for dogs to be used with standard therapy for the treatment of congestive heart failure (CHF) caused by valvular disease. (Other treatments can include pimobendan, digoxin, angiotensin-converting enzyme [ACE] inhibitors, and furosemide.)

Spironolactone can produce hyperkalemia in some patients. Facial dermatitis has been reported from administration of spironolactone to cats, which may limit its clinical use in these animals.

Spironolactone is often used together with ACE inhibitors, such as enalapril. It acts synergistically with ACE inhibitors and does not ordinarily produce adverse changes in potassium concentrations.

Question 89

Telmisartan
semintra
vasodilator

Answer 89

Telmisartan is a vasodilator that functions as an angiotensin II receptor blocker (ARB). Angiotensin II acts primarily on the type 1 and type 2 receptors, but telmisartan has high affinity and selectivity for the angiotensin II subtype 1 (AT-1) receptor and preserves the beneficial effects from the AT-2 subtype (angiotensin II, subtype 2 receptor).

In cats, telmisartan has an approved indication for treating hypertension in cats and has been shown to be superior to ACE inhibitors for this use. In dogs, telmisartan does not have an FDA-approved indication but is used to treat hypertension when other agents have been ineffective. Telmisartan is the only ARB that has been rigorously tested in cats. It was more effective than ACE inhibitors, irbesartan, and losartan. Compared with placebo, it significantly lowers the systolic blood pressure in cats after 14 days of treatment.

Adverse effects have been uncommon, but clinical trials in cats have shown vomiting, hypersalivation, weight loss, diarrhea, lethargy, anemia, and hypotension. Drugs that act on the RAAS can produce a decrease in red blood cell count.

Combined use of an ARB and an ACE inhibitor may increase the risk of kidney injury because of dual blockade. This may be associated with increased risks of hypotension, hyperkalemia, and changes in kidney function.

Question 90

Amlodipine (this is still used because sometimes cats don’t respond as hoped to telmisartan)
norvasc
calcium-channel

Answer 90

Calcium-channel blocking drug. Amlodipine is a second-generation calcium-channel blocker of the dihydropyridine class. It decreases calcium influx in cardiac and vascular smooth muscle. However, its greatest effect is on vascular smooth muscle by blocking the L-type calcium channels. Through this mechanism, it acts as a vasodilator for treating hypertension.

In both dogs and cats, amlodipine is effective for lowering systemic blood pressure. Therefore, it is used to treat systemic hypertension (high blood pressure). Amlodipine has been considered the drug of choice for many years by clinicians for treating hypertension in cats.

The most common adverse effect is hypotension. In dogs and cats, gingival hyperplasia has been observed, which may be caused by an up-regulation of circulating androgens or inhibition of transglutaminase. Other mechanisms may be involved but are speculative.

In both dogs and cats, amlodipine may activate the renin–angiotensin–aldosterone system (RAAS). When this occurs, ACE inhibitors may be somewhat effective in reducing activation of RAAS, but addition of this medication also may increase risk of hypotension and may decrease renal glomerular pressure.

Use cautiously with other vasodilators. Drug interactions are possible from concurrent use with phenylpropanolamine, theophylline, and beta-agonists. Concurrent use with ACE inhibitors may increase the risk of hypotension and decreased glomerular pressure.

Question 91

beta blockers: atenolol
tenormin
beta antagonist

Answer 91

Beta-adrenergic blocker. Relatively selective for beta1-receptor. Atenolol is a water-soluble beta blocker and relies on the kidneys for clearance. (By comparison, drugs such as propranolol and metoprolol are more lipophilic and rely on the liver for clearance.)

Atenolol is one of the most commonly administered beta blockers for dogs and cats. Atenolol is used primarily as an antiarrhythmic or for other cardiovascular conditions in which it is needed to slow the sinus rate. In cats, this drug is commonly used to treat heart disease from cardiomyopathy or hyperthyroidism, but it should not be used as monotherapy to treat primary hypertension.

Bradycardia and heart block are possible. Atenolol may produce bronchospasm in sensitive patients.

Atenolol is reported to be less affected by changes in hepatic metabolism than other beta blockers. Although it is not an FDA-approved drug for dogs and cats, dosing guidelines are based on published reports and experience of experts

Question 92

beta blocker: metoprolol
lopressor
beta block

Answer 92

Metoprolol is a beta1-adrenergic receptor blocker. Metoprolol has similar properties to propranolol except that metoprolol is specific for beta1 receptors, with less effect on beta2 receptors. Metoprolol is a lipophilic beta blocker and relies on the liver for clearance.

Metoprolol is used to control tachyarrhythmias and to control the response from adrenergic stimulation in animals. Beta blockers effectively slow heart rate. Metoprolol is used in animals in which it is important to control ventricular rate, decrease conduction through the atrioventricular (AV) and sinoatrial nodes, and improve diastolic function. In animals, it has been used for tachyarrhythmias, hypertrophic cardiomyopathy, atrial fibrillation, and other cardiac diseases.

Adverse effects are primarily caused by excessive cardiovascular depression (decreased inotropic effects). Metoprolol may cause AV block.

Question 93

esmolol ( emergency use)
brevibloc
beta blocker, antiarrhythmic

Answer 93

Esmolol is a short-acting beta-adrenergic blocker. It is most selective for the beta1 receptor. The difference between esmolol and other beta blockers is the short duration of action, which is attributed to metabolism by red blood cell esterases. It has a half-life of only 9–10 minutes; thus, it is impractical for long-term use.

Esmolol is indicated for short-term control of systemic hypertension and tachyarrhythmias. It has been used for emergency therapy or short-term treatment. Long-term treatment is not possible because of the short half-life. Ordinarily, if an animal shows a positive response to esmolol, it can be switched to longer-acting beta blockers (e.g., propranolol or atenolol).

Adverse effects related to beta1-blocking effects on the heart include myocardial depression, reduced cardiac output, and bradycardia.

Esmolol is indicated for short-term IV therapy only. Doses are based primarily on empiricism or extrapolation of human dose. No clinical studies have been reported in animals.

Question 94

Propranolol- probably not first choice
inderal
beta blocker

Answer 94

Propranolol is one of the oldest and widely used beta-adrenergic blockers. It is nonselective for beta1- and beta2-adrenergic receptors and newer drugs that are more specific are more commonly used. It is also a Class II antiarrhythmic that inhibits cardiac conduction in the atrioventricular and sinoatrial nodes to decrease heart rate and the ventricular response to atrial stimulation.

Propranolol is used primarily to decrease heart rate, decrease cardiac conduction, control tachyarrhythmias, and decrease blood pressure. It is effective in controlling the response from adrenergic stimulation. Beta blockers such as propranolol are among the most effective drugs for slowing heart rate, but propranolol is not used as commonly as other more specific agents such as atenolol or metoprolol.

The adverse effects from propranolol are related to beta1-blocking effects on heart. Propranolol causes cardiac depression and decreases cardiac output. Beta2-blocking effects can cause bronchoconstriction and decrease insulin secretion. Switch to a more specific beta1-blocker (see Instructions for Use) if beta2-blocking effects are undesirable and a more specific agent is needed. Weakness and fatigue can be caused by beta blockers, which can indicate that a reduction in dose is needed

Do not administer to animals with low cardiac reserve, bradycardia, or poor systolic function. Use cautiously in animals with respiratory problems because bronchoconstriction can occur from beta2 effects. Hyperthyroid cats may have reduced clearance and increased risk of toxicity.

Question 95

Pimobendan
inodilator
vetmedin
cardiac inotropic agent

Answer 95

Pimobendan is both a positive inotrope and a vasodilator. The vasodilator effects occur via inhibition of PDE III. PDE III is the enzyme that degrades cyclic adenosine monophosphate (cAMP); therefore, its action is to increase intracellular concentrations of cAMP. There may be some inhibition of PDE V in the pulmonary circulation. The inotropic effects of pimobendan are attributed to its action as a calcium sensitizer rather than the PDE inhibition.

Pimobendan is indicated for use in dogs for treatment of congestive heart failure (CHF). It has been used in dogs with either valvular insufficiency or cardiomyopathy. It is recommended in consensus guidelines for any dog with valvular disease with stage B2 or higher and may delay onset of CHF. In dogs with heart failure caused by valvular disease, it decreased heart rate, decreased left ventricular and left atrial dimensions, reduced heart size, and reduced preload and natriuretic peptide concentrations.

Pimobendan is potentially arrhythmogenic, but this effect (e.g., atrial fibrillation or ventricular arrhythmias) has been rare and seen primarily in animals with severe underlying cardiac disease.

Use pimobendan cautiously in animals prone to cardiac arrhythmias. Do not use in animals with obstructive cardiomyopathy or a fixed obstruction of the outflow tract. Compounded formulations will not achieve the same absorption profile in dogs as the proprietary form.

Evaluate stage of heart failure in animals before use. Consider the addition of other drugs such as ACE inhibitors, spironolactone, furosemide, and digoxin in animals as the severity of the heart disease increases.

Question 96

Furosemide- loop diuretic
lasix
diuretic

Answer 96

Furosemide is a loop diuretic that inhibits the Na+/K+/2Cl– cotransporter in the ascending thick loop of Henle. It is often called a high-ceiling diuretic because it is more effective than other diuretics. Furosemide decreases the sodium, chloride, and potassium reabsorption from the tubule.

In small animals, furosemide is the drug of choice to treat conditions that cause edema, including pulmonary edema, liver disease, heart disease, and vascular disease. It is recommended in dogs with clinical signs of stage C heart disease, to be used initially, until the patient’s clinical signs have improved. Furosemide increases potassium and calcium excretion and is used to treat hyperkalemia and hypercalcemia.

Adverse effects are primarily related to diuretic effect (loss of fluid and electrolytes). In dogs, hyponatremia is more common than hypokalemia. Tolerance and activation of the renin–angiotensin–aldosterone system (RAAS) occur with repeated administration, in which the diuretic effect is attenuated.

Recommendations for use of furosemide are based on extensive clinical use of furosemide in animals. The onset of effect after an injection is usually 5 minutes, with the peak at 30 minutes to 2 hours and a duration of approximately 2–4 hours. CRIs in dogs and horses can be more effective than intermittent bolus.

Question 97

Digoxin- cardiac glycoside
lanoxin and cardoxin
cardiac inotropic agent

Answer 97

Digoxin is a cardiac inotropic agent and also is used to regulate cardiac rate and rhythm. Digoxin increases cardiac contractility and decreases heart rate. The mechanism is via inactivation of cardiac muscle sodium–potassium ATPase and increased intracellular availability of calcium, triggering calcium release from sarcoplasmic reticulum.

The use of digoxin for animals in heart failure has declined significantly because pimobendan is more frequently used and is available in a veterinary formulation.
Digoxin has been used for treatment of heart failure in dogs, cats, and occasionally other animals. Because the use for an inotropic effect has declined, the most common use is to decrease the heart rate in animals.

Digitalis glycosides such as digoxin have a narrow therapeutic index. They may cause a variety of arrhythmias in patients (e.g., AV and ventricular tachycardia) and may produce delayed after depolarization-induced arrhythmias.

High potassium will diminish clinical effect; low potassium will enhance effect and toxicity. Because some animals may also be receiving diuretics, monitor the potassium concentrations during treatment.

Question 98

Dobutamine
dobutrex
cardiac inotropic agent

Answer 98

Dobutamine is a potent adrenergic agonist. Dobutamine is a racemic mixture (R and S isomers) that has both beta1- and beta2-adrenergic activity. However, its most important clinical effects are caused by the relative cardioselective agonist activity on beta1 receptors.

Dobutamine is used primarily for the acute treatment of heart failure. It produces an inotropic effect without increasing heart rate. It is usually administered for short-term treatment of heart failure when hospitalization is required (e.g., Class C heart failure class).

Dobutamine may cause tachycardia and ventricular arrhythmias at high doses or in sensitive individuals. If tachycardia or arrhythmias are detected, stop the infusion rate and resume at a lower rate. In horses, 2 mcg/kg/min can cause a significant increase in systemic blood pressure in conscious horses.

Dobutamine has a rapid elimination half-life (minutes) and therefore must be administered via carefully monitored CRI. Dose rates (infusion rate) can be adjusted by monitoring patient response. In dogs, doses as low as 2 mcg/kg/min have improved cardiac output.

Question 99

hydralazine arterial- vasodilator
apresoline
vasodilator

Answer 99

Hydralazine is a vasodilator used when patients have become refractory to other vasodilators. Hydralazine relaxes vascular smooth muscle and reduces blood pressure. In arteriolar vascular beds, it relaxes vascular smooth muscle to reduce vascular resistance and improves cardiac output.

Hydralazine is used to dilate arterioles and decrease cardiac afterload. It is primarily used for treatment of congestive heart failure (CHF), valvular disease of the heart, and other cardiovascular disorders characterized by high peripheral vascular resistance.

Adverse effects are attributed to excess vasodilation and subsequent hypotension, which results in reflex tachycardia. Hydralazine may dangerously decrease cardiac output if not monitored carefully.

Use of hydralazine in heart failure may accompany other drugs, such as digoxin, pimobendan, ACE inhibitors, and diuretics. The optimum dosage in animals may be adjusted by monitoring blood pressure.

Question 100

nitroglycerin-venous dilator
vasodilator
nitrol, nitro-bid, and nitrostat

Answer 100

Nitroglycerin is a nitrate nitrovasodilator. Like other nitrovasodilators, it relaxes vascular smooth muscle (especially venous) through generation of nitric oxide (NO). The nitrate vasodilators are esters of nitrous acid. They are metabolized to inorganic nitrite and denitrated metabolites. Nitrites, organic nitrates, and nitroso compounds all act to activate the enzyme guanylate cyclase, which in turn produces cyclic guanosine monophosphate (GMP) in vascular smooth muscle and relaxes smooth muscle. NO is also known as the endothelium-derived relaxing factor.

Nitroglycerin, like other nitrovasodilators, is used primarily in heart failure or pulmonary edema to reduce preload or decrease pulmonary hypertension. Nitrates relax smooth muscle in both arteries and veins, but they are often used clinically as preload reducers.

Tolerance can develop with repeated chronic use. Tolerance may be caused by a progressive depletion of sulfhydryl groups necessary for the formation of NO. Efficacy is improved if the drug is used intermittently instead of continuously because intermittent use allows time for regeneration of sulfhydryl groups.

Question 101

clopidogrel
plavix
anti-platelet drug

Answer 101

Clopidogrel is a platelet inhibitor. It is a thienopyridine and inhibits adenosine diphosphate (ADP) receptor–mediated platelet activity. Clopidogrel is metabolized to an active metabolite that exerts its antiplatelet effect

Clopidogrel is used to inhibit platelets in patients that are prone to forming blood clots. In patients with a high risk for thrombi and emboli, clopidogrel inhibits mechanisms that are not affected by aspirin alone.

Bleeding problems can occur in susceptible patients, but this has not been reported to be a clinical problem in dogs or cats. In people, pruritus and skin rash have been reported, but this has not been observed in dogs and cats. The taste is bitter, and some cats may refuse oral administration.

Question 102

darbepoetin
aranesp
hormone

Answer 102

Human recombinant erythropoietin. Hematopoietic growth factor that stimulates erythropoiesis. Darbepoetin is a hyperglycosylated recombinant form of human erythropoietin. It differs from epoetin because it has 5 N-carbohydrate chains, thus producing a longer duration. The longer half-life translates to less often administration.

Darbepoetin alfa is used to treat nonregenerative anemia. It has been used to treat myelosuppression caused by disease or chemotherapy. It has been used in people to treat anemia associated with chronic kidney disease (CKD) and has been used for this purpose in dogs and cats with CKD.

Injection-site pain and headache have occurred in people. Adverse effects have included iron deficiency, hypertension, joint pain (arthralgia), gastrointestinal (GI) disturbance, and polycythemia. Because this product is a human-recombinant product, it may induce local and systemic allergic reactions in animals.

The use of darbepoetin has been primarily in cats and dogs with anemia caused by CKD. It is preferred over epoetin alpha for this use. Iron supplementation is recommended when used in cats and dogs. By improving anemia, it may increase survival in animals with CKD and improve quality of life.

Question 103

Erythropoietin
hormone

Answer 103

Epoetin alfa is a human recombinant form of erythropoietin. Erythropoietin is a hematopoietic growth factor that stimulates erythropoiesis. It is used in clinical patients where stimulation of red blood cell production is needed.

Epoetin alfa is used to treat nonregenerative anemia. It has been used to treat myelosuppression caused by disease or chemotherapy. It also has been used to treat chronic anemia associated with chronic renal failure. The value of epoetin alpha to improve anemia in cats with chronic renal failure has been established in several studies.

Because this product is a human-recombinant product, it may induce local and systemic allergic reactions in animals. Injection-site pain and headache have occurred in people. Seizures also have occurred.

The use of epoetin alfa has been limited primarily to dogs and cats. The only form currently available is a human-recombinant product. It is used in animals when hematocrit falls below 25%. In cats, 100 units/kg SQ three times a week is administered until a target hematocrit of 30%–40% is attained. Thereafter, twice-weekly injections are used.

Question 104

mexiletine
anti arrhythmic

Answer 104

Mexiletine is an antiarrhythmic drug used occasionally in dogs. Mexiletine is a Class IB antiarrhythmic agent. Mechanism of action is to block the fast sodium channel and depress Phase 0 of depolarization.

Mexiletine has been used to treat ventricular arrhythmias. Although lidocaine is often the first Class I antiarrhythmic agent used for injection in the hospital, when longer-term treatment with an oral drug is needed, mexiletine is often the first choice.

In dogs, the most common adverse effects are GI problems. High doses may cause excitement and tremors. Mexiletine can be arrhythmogenic in some animals. In people, related drugs (flecainide and encainide) can be proarrhythmogenic and associated with excessive mortality.

Question 105

sotalol
betapace
beta blocker, antiarrhythmic

Answer 105

Sotalol is an antiarrhythmic agent that has effects as a nonselective beta-receptor (beta1 and beta2) adrenergic blocker (Class II antiarrhythmic). The action as a Class II antiarrhythmic is similar to propranolol (one-third potency); however, it has beneficial effects through additional antiarrhythmic effects.

Sotalol is indicated for control of refractory ventricular arrhythmias. It has also been used for refractory atrial fibrillation. Although sotalol has been used as a preferred oral antiarrhythmic agent administered to small animals, particularly dogs, there are no controlled studies to establish efficacy over other agents

Adverse effects have not been reported for animals but are expected to be similar to those of propranolol. In people, reported adverse effects include atrioventricular (AV) block, hypotension, dyspnea, bronchospasm, bradycardia, and QT interval prolongation.

Adverse effects have not been reported for animals but are expected to be similar to those of propranolol. In people, reported adverse effects include atrioventricular (AV) block, hypotension, dyspnea, bronchospasm, bradycardia, and QT interval prolongation.

The beta-blocking effects occur at low doses; Class III antiarrhythmic effects occur at higher doses. In people, sotalol has been a more effective maintenance agent for controlling arrhythmias than other drugs, and this may be true in animals also.

Question 106

lidocaine
xylocaine and generic brands
local anesthetic, anti arrhythmic

Answer 106

Lidocaine is a common local anesthetic. Lidocaine inhibits nerve conduction via sodium channel blockade. Lidocaine is also a Class 1 antiarrhythmic and decreases phase 0 depolarization without affecting conduction. After systemic administration, lidocaine is metabolized to monoethylglycinexylidide (MEGX), which also has antiarrhythmic properties. Lidocaine also has analgesic properties after systemic administration.

Lidocaine is used commonly as a local anesthetic and for treatment and conversion of ventricular arrhythmias. Lidocaine should be used cautiously for treating supraventricular arrhythmias because it may increase cardiac conduction. Lidocaine has been used on a limited basis to treat seizures that are refractory to other drugs.

High doses of lidocaine cause CNS effects (tremors, twitches, and seizures) and vomiting, but the risk of lidocaine-induced seizures is low. IV use and CRIs in horses have caused muscle fasciculations, rapid eye blinking, anxiety, ataxia, weakness, and seizures. Lidocaine can produce cardiac arrhythmias, but it has greater effect on abnormal cardiac tissue than normal tissue.
Use lidocaine cautiously in cats. IV doses of lidocaine in cats have resulted in death. In cats under anesthesia, lidocaine administration has caused decreased cardiac output, cardiovascular depression, and decreased oxygen delivery to tissues. In cats, lidocaine has also produced methemoglobinemia and hemolysis.

Question 107

digoxin
lanoxin cardoxin
cardiac inotropic agent

Answer 107

Digoxin is a cardiac inotropic agent and also is used to regulate cardiac rate and rhythm. Digoxin increases cardiac contractility and decreases heart rate. The mechanism is via inactivation of cardiac muscle sodium–potassium ATPase and increased intracellular availability of calcium, triggering calcium release from sarcoplasmic reticulum. Beneficial cardiac effects may be caused by decreased heart rate and suppression of the AV node to inhibit reentrant cardiac arrhythmias via these neuroendocrine effects.

The use of digoxin for animals in heart failure has declined significantly because pimobendan is more frequently used and is available in a veterinary formulation.
Digoxin has been used for treatment of heart failure in dogs, cats, and occasionally other animals. Because the use for an inotropic effect has declined, the most common use is to decrease the heart rate in animals. This property is used for treatment of supraventricular arrhythmias to decrease ventricular response to atrial stimulation via suppression of the AV node.

Digitalis glycosides such as digoxin have a narrow therapeutic index. They may cause a variety of arrhythmias in patients (e.g., AV and ventricular tachycardia) and may produce delayed after depolarization-induced arrhythmias. Heart block (AV block) is possible. Digoxin frequently causes vomiting, anorexia, and diarrhea. Digoxin adverse effects are potentiated by hypokalemia and reduced by hyperkalemia.

Question 108

diltiazem
cardizem dilacor
calcium channel blocker

Answer 108

Diltiazem is a calcium-channel blocking drug. Diltiazem blocks calcium entry into cells via blockade of voltage-dependent slow calcium channel. Via this action, it produces vasodilation, negative chronotropic effects, and negative inotropic effects. However, the action on cardiac tissue (sinoatrial [SA] node and AV node)

Diltiazem is used primarily for control of supraventricular arrhythmias, atrial fibrillation, and hypertrophic cardiomyopathy. It also is used for atrial flutter, AV nodal reentry arrhythmias, and other forms of tachycardia. Diltiazem is more effective on heart tissues (AV node and SA node) than on blood vessels.

Hypotension, myocardial depression, bradycardia, and AV block are the most important adverse effects. If acute hypotension occurs, treat with aggressive fluid therapy and administration of calcium gluconate or calcium chloride. It may cause anorexia in some patients.

Question 109

atropine
generic brands
anticholinergic

Answer 109

Anticholinergic agent (blocks acetylcholine effect at muscarinic receptors), parasympatholytic.
As an antimuscarinic agent, it blocks cholinergic stimulation and causes decrease in GI motility and secretions, decrease in respiratory secretions, increased heart rate (antivagal effect), and mydriasis.

Atropine is used primarily as an adjunct to anesthesia or other procedures to increase heart rate and decrease respiratory and GI secretions. Atropine is the drug of choice to overcome excess vagal stimulation associated with some clinical conditions. Atropine is used during cardiac arrest to overcome vagal influences.

Side effects include xerostomia, ileus, constipation, tachycardia, and urine retention

Atropine is used ordinarily as an adjunct with anesthesia or other procedures. Compared with lower doses, in dogs, 0.06 mg/kg was more effective than 0.02 mg/kg. Atropine may be used during cardiac resuscitation; however, high doses may cause sustained tachycardia and increased myocardial oxygen demand.

Question 110

proparacaine

Answer 110

Proparacaine is a rapid-acting topical anesthetic used to desensitize the cornea for ophthalmic procedures. It is available as a 0.5 percent solution that is applied in drop doses every 5 to 10 min-utes for a maximum of seven doses. Proparacaine provides 5 to 10 minutes of anesthesia to the cornea with limited drug penetration to the conjunctiva

Question 111

fluorescein

Answer 111

Fluorescein may temporarily stain fur, skin, and clothing. The fluorescein strip should not be allowed to touch the cornea, as it will cause stain retention at the site of contact. This will result in false positive readings.

fluorescein adheres to the water-soluble stroma layer when the dye is rinsed with sterile saline. Defects in the corneal epithelium will be green, while deep corneal lesions (descemetoceles) may not take up stain and will appear black.

Question 112

tropicamide

Answer 112

tropicamide, an acetylcholine receptor blocker, is used for fundic examination (Figure 18-8B). It is a rapid-acting mydriatic and has a slight cycloplegic effect. It has a more rapid onset and shorter duration of action than atropine, making it a more desirable diagnostic agent. Its adverse effects include local discomfort and dry mouth. It is contraindicated in animals with glaucoma or KCS for the same reasons as atropine.

Question 113

Latanoprost

Answer 113

Latanoprost ophthalmic is used to treat glaucoma (a condition in which increased pressure in the eye can lead to gradual loss of vision) and ocular hypertension (a condition which causes increased pressure in the eye). Latanoprost is in a class of medications called prostaglandin analogs. It lowers pressure in the eye by increasing the flow of natural eye fluids out of the eye.

Question 114

scopolamine

Answer 114

Scopolamine ophthalmic causes the muscles in your eye to become relaxed. This widens your pupil. Your pupil will remain wide and will not respond to light.

Scopolamine ophthalmic is used to dilate (widen) your pupil when you have an inflammatory condition or in diagnostic or postsurgery situations in which this effect may be helpful.

Do not use scopolamine ophthalmic if you have glaucoma that is not being treated.

Scopolamine ophthalmic eye drops contain a preservative (benzalkonium chloride), so do not wear soft contact lenses when the eye drops are being inserted.

Question 115

travoprost

Answer 115

Travoprost ophthalmic is used to treat glaucoma (a condition in which increased pressure in the eye can lead to gradual loss of vision) and ocular hypertension (a condition which causes increased pressure in the eye). Travoprost is in a class of medications called prostaglandin analogs. It lowers pressure in the eye by increasing the flow of natural eye fluids out of the eye

Question 116

dorzolamide

Answer 116

Ophthalmic dorzolamide is used to treat glaucoma, a condition in which increased pressure in the eye can lead to gradual loss of vision. Dorzolamide is in a class of medications called carbonic anhydrase inhibitors. It works by decreasing the pressure in the eye.

Question 117

timolol

Answer 117

Beta-adrenergic blockers such as timolol are marketed in a variety of concentrations and different formulations; therefore, it is important to know which you are administering to prevent complications in patients. (E) Alpha-ad-renergic agonists such as brimonidine decrease intraocular pressure by reducing aqueous humor secretion and are marketed in a range of concentrations.

Question 118

mannitol
osmitrol
diuretic

Answer 118

Mannitol is used as a hyperosmotic diuretic. Mannitol occurs naturally as a sugar in fruits and vegetables. As an osmotic diuretic, mannitol is freely filtered by the glomerulus, but it is not reabsorbed by the renal tubule. Therefore, it increases osmolality of the urine.

Mannitol is administered intravenously for treatment of cerebral edema, acute glaucoma, and conditions associated with tissue edema. Other agents are preferred for management of glaucoma, but mannitol can be administered in refractory cases.

Mannitol produces a profound diuresis and can cause significant fluid loss and electrolyte imbalance. An administration rate that is too rapid may expand the extracellular volume excessively.

Do not use in patients who are dehydrated. Use cautiously when intracranial bleeding is suspected because it may increase bleeding. (This effect is controversial when dealing with intracranial hemorrhage.)

Question 119

cyclosporine
immunosuppressive drug

Answer 119

Cyclosporine is a commonly used immunosuppressive drug. Cyclosporine binds to a specific cellular receptor on calcineurin and inhibits the T-cell receptor–activated signal transduction pathway. Particularly important are its effects to suppress interleukin-2 (IL-2) and other cytokines (e.g., IL-4 and tumor necrosis factor–alpha) and block proliferation of activated T lymphocytes. The action of cyclosporine is more specific for T cells compared with B cells and affects both helper T cells and cytotoxic T cells. Production of autoantibodies by B cells may be suppressed because this process requires the help of activated T cells. Therefore, calcineurin inhibitors such as cyclosporine may decrease humoral immune response by interfering with T-helper cells instead of interfering directly.

Systemic uses (usually oral) for cyclosporine include IMHA, atopic dermatitis in dogs, and perianal fistulas. Other diseases have been treated with cyclosporine, such as sebaceous adenitis, idiopathic sterile nodular panniculitis, vesicular cutaneous lupus erythematosus, IMHA, immune-mediated thrombocytopenia, IBD, immune-mediated polyarthritis, myasthenia gravis, idiopathic chronic hepatitis, and aplastic anemia. It has also been used for treatment of granulomatous meningoencephalitis (3–6 mg/kg q12h). For many of these indications, efficacy has not been established through well-controlled clinical studies, and the use is based on anecdotal experience and recommendations from clinical experts.

The most common adverse effects in dogs and cats are GI problems (vomiting, diarrhea, anorexia, and weight loss). Vomiting is often observed only during initial treatment and may be transient. Hypersalivation has been observed in cats. Cyclosporine may induce shedding of hair and stimulate new hair growth in dogs of a different consistency. Neurotoxicity from high doses has been seen in dogs, which can be seen as tremors.

Question 120

trifluridine

Answer 120

Structurally similar to thymidine and inhibits DNA synthesis by substituting itself for thymidine in replicating viral DNA
Used to treat FHV-1 keratitis in cats • Has been used to treat equine herpes virus keratitis in horses
• May cause ocular irritation that may appear more intense than the inflammation caused by the actual virus
• Used as an ophthalmic solution that needs to be administered frequently

Question 121

So many macrocyclic lactones approved for veterinary use! What are their names?

Answer 121

ivermectin, moxidectin,selamectin, doramectin, eprinomectin, milbemycin