Ch.8 GI Drugs Flashcards
Underlying causes of GI disease
-infectious sources, dietary excess, adverse drug effects, systemic disease
Clinical signs of GI disease
diarrhea, constipation, vomiting, bloat, ulcer development, or pain
The term Gi tract describes a long, muscular tube that begins and ends at
begins at the mouth and ends at the anus
3 basic control systems that the GI tract is under
- Autonomic nervous system
2.GI hormones - Special substances (histamine, serotonin, prostaglandin)
Parasympathetic stimulation _ intestinal motility, _ GI secretions and relaxes sphincters
increases
GI hormones that are released from intestinal cells and cause gastric secretion and emptying, as well as emptying of the gallbladder
gastrin, secretin, cholecystokinin
vomiting is initiated by activation of the
emetic center in the brain
Vomiting impulses
Peripheral receptors- irritation,
Cerebral cortex- pain, excitement, fear
CRTZ-disturbances of inner ear, drugs, metabolic conditions
Emetics are drugs that _ _ and are used in the tx of
induce vomiting; poisoning and drug overdose
When should vomiting not be induced
if caustic substances have been ingested
Who should you always check with before inducing vomiting
poison control
_ _ is given if emesis is contraindicated (it absorbs many chemicals and drugs in the upper GI tract)
activated charcoal
Emetics can be _ acting (working on the CRTZ) or _ acting (working on receptors locally)
centrally; peripherally
Centrally acting emetics
Apomorphine- dogs (poorly absorbed PO)
Xylazine- cats
Peripherally acting emetics
Ipecac syrup
Home remedies
Hydrogen peroxide 1ml/lb, not for cats due to hemorrhagic gastritis and esophagitis
Antiemetics are drugs that
control vomiting, help alleviate discomfort and help control electrolyte balance
Examples of antiemetics
-Phenothiazine derivatives
-Antihistamines
-Anticholinergics
-Procainamide derivatives
-Serotonin receptor antagonists
-NK-1 Receptor antagonists
Phenothiazine derivatives used as antiemetics act _: inhibit dopamine receptors in the chemoreceptor trigger zone, thus decreasing the stimulation to vomit
centrally
Examples of phenothiazine derivatives and side effects
-Chlorpromazine
-Prochlorperazine
-Acepromazine
SE: hypotension and sedation
Antihistamines work as an antiemetic by blocking
input from the vestibular system to the CRTZ through H1 blockade
Antihistamines control vomiting when the vomiting is due to
motion sickness, vaccine rxns, inner ear problems
Examples of antihistamines used as antiemetics
-Dimenhydrinate
-Diphenhydramine
-Meclizine
-Promethazine (phenergan)
procainamide derivatives should not be used in animals with
GI obstructions, GI perforation, or GI hemorrhage (metoclopramide)
Serotonin receptor antagonists work on the theory that some
chemicals cause vomiting because they increase serotonin release from small intestinal cells (ondansetron aka zofran)
Maropitant citrate (cerenia) is used to prevent _ _ and _ _
acute vomiting and motion sickness
Side effects of Maropitant citrate (cerenia)
pain at injection site, anorexia, hyper salivation, and diarrhea
Gastric ulceration may occur as a side effect of which drugs
NSAIDS, corticosteriods
Clinical signs of gastric ulceration
hematemesis, pain melena
Tx of gastric ulcers will decrease _ and control _
acid; CS
Antiulcer drug categories
-Histamine 2 receptor antagonists
-Proton pump inhibitors
-Antacids
-Mucosal protective drugs
-Prostaglandin analogs
Histamine-2 receptor antagonists prevent acid reflux by
competitively blocking the H2 receptors of the parietal cells in the stomach, thus reducing gastric secretion
examples of histamine-2 receptor antagonists as anti ulcer drugs
Cimetidine (Tagamet)
Ranitidine (Zantac)
Famotidine (Pepcid)
Proton pump inhibitors as anti ulcer drugs inhibits ion transport into the stomach so that it cannot
secrete HCI
Examples of proton pump inhibitors
Omeprazole (Prilosec)
Lansoprazole (Prevacid)
Antacids promote ulcer healing by
neutralizing HCI
Why must antacids be given within 1-2 hours of other medications?
they interact with other drugs (may inhibit their absorption)
Examples of antacids
-aluminum/ magnesium hydroxide
-magnesium hydroxide
-calcium carbonate
Mucosal protective drugs combine with protein to form an adherent substance that covers the
ulcers and protects it from stomach acid and pepsin (ex: sucralfate)
Mucosal protective drugs must be given 30min-1 hour _ H2 antagonists
before
What do prostaglandin analogs do
suppress gastric secretions and increase mucus production in the GI tract (ex: misoprostol, which is usually given to animals taking NSAID)
Antidiarrheals are drugs that
decrease peristalsis, thereby allowing fluid absorption from the intestinal contents
Examples of antidiarrheals
-Narcotics
-Anticholinergics
-Protectants/absorbents
-Probiotics
-Metronidazole
Opiate-related agents control diarrhea by
decreasing both intestinal secretions and the flow of feces and increasing segmental contractions
Examples of opiate related agents
Diphenoxylate (lomotil)
Loperamide (lmodium)
Paregoric/ kaolin/ pectin (parepectolin)
Side effects of opiate related agents as antidiarrheals
CNS depression, ileus, urine retention, bloat, constipation
What do protectants/ absorbents do
coat inflamed intestinal mucosa w/ a protective layer (protectants) or bind bacteria and/or digestive enzymes and/or toxins to protect intestinal mucosa from damaging effects (absorbents)
Examples of protectants/absorbents
Bismuth subsalicylate (caution in cats)
Kaolin/pectin
Activated charcoal
Toxiban
Side effects of protectants/absorbents
constipation, dark stool
Probiotics seed the GI tract with beneficial _; use is based on the theory that some forms of diarrhea are caused by disruption of the normal bacterial flora of the GI tract
bacteria
Examples of probiotics
plain yogurt w/ active cultures
variety of trade-name products
A theory regarding the development of diarrhea is that _ bacteria may increase due to disruption of normal GI flora
anaerobic (metronidazole is an example of an antibiotic used to tx diarrhea)
What do laxatives do
loosen bowel contents and encourages evacuation of stool
Saline/Hyper-osmotic laxatives pull water into the colon and increase water content in the feces, thereby increasing
bulk and stimulating peristalsis
Saline/Hyper-osmotic laxatives are salts or saline which may cause
electrolyte imbalances if absorbed systemically
Examples of saline/hyper-osmotic laxatives and side effects
-lactulose
-sodium phosphate w/ sodium biphosphate
-magnesium sulfate
-magnesium hydroxide
SE: cramping, vomiting, electrolyte imbalances (esp. cats)
Stimulant/irritants increase peristalsis by
chemically irritating sensory nerve endings in the intestinal mucosa
Examples of stimulant/irritants as laxatives
bisacodyl (dulcolax)
castor oil
Bulk-forming laxatives absorb water into the intestine, increase fecal bulk, and stimulate peristalsis, resulting in
large, soft stool production (which tends to look normal)
Examples of bulk-forming laxatives
Metamucil, psylliums, bran
Emollients/Surfactants/Stool softeners reduce surface tension and allow
water to penetrate the GI contents, softening stool
Emollients/Surfactants/Stool softeners can be
stool softeners, lubricants, fecal wetting agents
Examples of Emollients/Surfactants/Stool softeners
decusate sodium, decusate calcium, decusate potassium, petroleum products
Phosphate enemas should not be used in
cats or puppies bc of the potential to cause electrolyte abnormalites
Lubricants typically oils that
soften fecal mass to make it easier to move through the GI tract (ex: mineral oil, laxatone)
Prokinetic agents increase
motility of parts of the GI tract to enhance movement of material through it
Dopaminergic agents stimulate
gastroesphogeal sphincter, stomach, and intestinal (ex: metoclopramide and domperidone)
Serotonergic agents stimulate
motility of gastroesphogeal sphincter, stomach, small intestine, and colon (ex: cisapride)
Bloody diarrhea may warrant _ use
antibiotic
Most commonly used antibiotic for GI disease is
metronidazole
Why are antibiotics not routinely used for GI issues
cause damage to normal flora
Anti-inflammatory agents that may be used for immune mediated disease/ inflammatory bowel disease
Prednisone/Prednisolone
Azathioprine
Sulfasalazine
Antifoaming drugs are used in ruminants whose rumens are subject to
acute frothy bloat
Antifoaming agents examples
poloxalene and polymerized methyl silicone
Pancreatic enzymes must be supplemented in the diet when the
pancreas is not function properly (as in pancreatic exocrine insufficiency)
Pancrealipase contains:
primarily lipase but also contains amylase and protease
Enzyme supplements can be irritating to the
skin on contact and to nasal passages upon inhalation
Serotonin antagonist antihistamines promote appetite by
inhibition at the serotoninergic receptors which control satiety
SE: sedation and dry mouth
Ex: cyproheptadine
Benzodiazepines are effective appetite stimulants in _ but not _
cats; dogs
SE:sedation and ataxia
Ex: Diazepam
Tetracyclic antidepressants stimulate appetite by antagonizing
alpha2 receptors
SE: sedation, vocalization
Ex: Mirtazipine
