GI Drugs Flashcards
Which hormones stimulate appetite?
- Norepinephrine
- Dopamine
- GABA
Which hormone inhibits appetite?
Serotonin
Appetite stimulant are a therapy for what?
Anorexia/Hyporexia
Name two GABA agonists.
- Benzodiazepines
2. Propofol
Name 2 serotonin (5-HT) antagonists.
- Cyproheptadine
2. Mirtazapine
Name four misc. appetite stimulants.
- Glucocorticoids (Prednisone)
- B-vitamins
- Megestrol acetate
- Anabolic steroids
What is the MOA of benzodiazepines?
They act by stimulating GABA and inhibiting the satiety center to increase appetite.
Are benzodiazepines more effective in dogs or cats?
Cats
How long should benzodiazepines be used?
Short term
What is the most common side effect with benzodiazepines?
Sedation
How are diazepam and midazolam administered?
- Diazepam is administered IV only (IM is painful)! Also, it should not be given orally to cats (idiosyncratic hepatoxicity)
- Midazolam can be administered IM.
What is the MOA of Propofol and what is one adverse effect?
Stimulates GABA and inhibits 5-HT. The drug should be given for a short period of time and its effect is seen at sub-hypnotic doses. One adverse effect is that Propofol causes Heinz body anemias in cats.
What are two serotonin (5-HT) antagonists?
- Cyproheptadine
- Effective in cats, given orally, and causes sedation. - Mirtazapine
- MOA: blocks 5-HT1 and 5-HT2 receptors.
- Used more often in dogs
Glucocorticoids have _____ feedback on corticotropin releasing hormone (CRH).
Negative
B-vitamins are used primarily for what?
Correcting deficiencies and stimulating appetite.
What drug has glucocorticoid activity to help stimulate appetite?
Megestrol acetate
What is the most commonly used peripheral emetic?
Hydrogen Peroxide 3%
What is the use for hydrogen peroxide and when don’t you use it?
- Direct irritation of oropharynx/GI lining
- Used for immediate vomiting
- Do NOT use in cats (hemmorhagic gastritis)
In the body, who centrally controls vomiting?
Emetic center inside the BBB and the CRTZ outside of the BBB.
Who has peripheral control of vomiting?
- Glossopharyngeal nerve
- Vagal afferents in the GIT
- Sympathetic afferents in viscera
What are six hormones that control vomiting?
- Serotonin
- Neurokinin
- Adrenergics
- Dopamine
- Histamine
- Toxins
What kind of emetic is Apomorphine, what are its uses, and what are its adverse effects?
Apomorphine is a centrally acting emetic that is used in dogs to stimulate dopamine receptors.. It can be given by all routes. Overdose can cause respiratory depression. Naloxone reveres Apomorphine’s effect, but it will not reverse the emetic effect.
What are 2 centrally acting emetics?
Apomorphine and Xylazine/Dexmedetomidine
Which central emetic is an a2 agonist and works more effectively in cats?
Xylazine/Dexmedetomidine
What is the MOA of neurokinin inhibitors (NK1 antagonists)?
Antagonists at NK1 receptors that block substance P and reduce its contribution to vomiting. Works centrally at the emetic center and the CRTZ.
What do you use Maropitant citrate for?
Prevention of motion sickness in dogs or treatment of acute vomiting in dogs and cats. Stings on injection.
Which drug do you use to treat ‘Old dog vestibular disease’?
Meclizine
When do you use Dimenhydrinate?
Use to prevent motion sickness when traveling.
What effect do antihistamines have on the CRTZ?
Reduced vestibular input to the CRTZ.
What are two anti-emetic dopamine antagonists? Which is more potent?
Metoclopramide and Phenothiazines.
Metoclopramide is more potent.
Which drug antagonizes Apomorphine induced emesis?
Metoclopramide
What are two phenothiazine drugs?
Chlorpromazine and prochlorperazine
What anti-emetic effect do chlorpromazine and prochlorperazine have?
They cause less sedation than other phenothiazines.
Name two serotonin antagonists.
Ondansetron and Dolasetron
What are some effects of Ondansetron and Dolasetron?
- Act on serotonin receptors centrally and peripherally.
- Initially used for chemo related nausea.
- More potent than metochlopromide but more expensive.
What is one antimuscarinic (M1) receptor antagonist that is not commonly used anymore?
N-butylscopalammonium bromide
What are some peripheral anti-emetics?
- Gastroprotectants
- Demulcents
- Antacids
- Prokinetics
What are four H2 blockers that are used as antacids?
- Cimetidine
- Ranitidine
- Nizatidine
- Famotidine
What are two proton pump inhibitors?
Omeprazole and Pantoprazole
What is one prostaglandin analog?
Misoprostol
What is one gastroprotectant?
Sucralfate
What do antihistamine H2 blockers do?
Inhibit gastric acid and pepsin secretion.
What does Cimetidine do as an antihistamine H2 blocker?
It has a short duration and inhibits microsomal enzymes.
T/F: Famotidine is more potent than Cimetidine.
True
Which two antihistamine H2 blockers have some pro kinetic activity?
Ranitidine and Nizatidine
What is the MOA for proton pump inhibitors?
Irreversibly inhibits H+/K+/ATPase proton pump resulting in decreased hydrochloric acid production.
T/F: H2 blockers are more potent that proton pump inhibitors.
False
How are omeprazole and lansoprazole administered?
Omeprazole = orally Lansoprazole = injectable
What is the MOA of Misoprostol?
Inhibits cAMP resulting in decreased protein kinase activity and hydrogen ion concentration but less potent than H2 or PPI. It increases mucus and sodium bicarb secretion and stimulates ulcer healing (COX-1).
When would you use Misoprostol?
Use it to treat NSAID-induced gastric ulcers.
What are some adverse effects of Misoprostol?
It stimulates uterine contractions causing abortions and can cause diarrhea.
What is the MOA of Sucralfate?
Binds to ulcer site and protects it against acid, pepsin and bile. It requires an acidic environment to bind to mucosae. It may stimulate PGs and antioxidants and increase mucosal blood flow.
What is a side effect of Sucralfate?
Constipation
What is one systemic antacid?
Sodium bicarb
What are some oral antacids and what do they do?
- Aluminum, magnesium and calcium
- Bind phosphorus in the gut and can cause constipation
- Aluminum hydroxide inactivates pepsin and binds to bile salts; may stimulate PGs.
What is a pro kinetic?
It affects the esophagus, stomach, small intestine and large intestine. Prokinetics increase the motility of the gut wall and decrease the time that it takes to move the fluid through the gut. Gut activity is increased by the PNS and is decreased by the SNS.
What is the MOA of Metoclopramide?
Dopamine antagonist; it sensitizes GI smooth muscle to acetylcholine. It also stimulates gastric motility and peristalsis in the duodenum and jejunum. Lastly, it has some anti-emetic effect.
What is the MOA of Domperidone?
Dopamine antagonist; acts centrally and peripherally, causing less CNS penetration.
What are the MOA for Cisapride and Mosapride?
Serotonin agonists; increase PNS input; block dopamine.
Which drug treats megacolon and megaesophagus in cats?
Cisapride
Which drug stimulates motility of the SI and cecum in horses?
Mosapride
Which two drugs inhibit acetycholinesterase?
Ranitidine and Nizatidine
What is erythromycin?
An antibiotic that binds with motilin receptors to stimulate peristalsis.
Which drugs are not very useful for GI disease and cause GI side effects?
Bethanechol (direct) and Neostigmine (indirect)
What are three GI protectants and what do they do?
- Bismuth subsalicylate - turns stool dark/black
- Activated charcoal
- Calcium carbonate
What is the MOA for anticholinergics? (ex: Neostigmine, Pyridostigmine, etc.)
Block muscarinic receptors in the GIT to inhibit motility and secretions. Usually labeled as an antispasmodic. Inhibiting motility can worsen diarrhea in some cases.
______ is used in horses for diarrhea, since Neostigmine and Pyridostigmine are contraindicated.
Aminopentamide
What is an emollient laxative and what are some examples?
Emollient laxatives are mechanical surfactants/stool softeners. Some examples include: Laxatone, mineral oil, and Felilax.
What is a simple bulk laxative? What is the most common one?
A simple bulk laxative absorbs water and swells; it reflexes GI movement. The most common drug is Psyllium.
What is an osmotic cathartic and what is the most common one?
An osmotic cathartic is nonabsorbed particles that attract water into the GI lumen. The most common is Polyethylene Glycol.
What is an irritant cathartic and what is the most common one?
Irritant cathartics irritate the GI to stimulate motility and secretion. The most common one is Bisacodyl.
What is one important thing to remember about enemas?
Never use phosphate containing enemas in cats!
What are three treatments that you can give an animal with Exocrine Pancreatic Insufficiency (EPI)?
Viokase, Pancreazyme and Raw Pancreas.
Out of the three treatments for EPI, which has the best efficacy and which is cheaper but less consistent?
Viokase has the best efficacy and raw pancreas is cheaper but not as consistent.
If the pancreatic enzymes are breaking down in an animal with EPI, what can you give to alleviate that?
H2 blockers
What is lactulose?
Ion traps ammonia in the colonic lumen to enhance removal from the body.
What drug can you use for bile replacement?
Ursodiol