Antiemetics and Prokinetics Flashcards
Maropitant
MOA: neurokinin-1 receptor antagonist - blocks the action of substance P in the CNS and at peripheral receptors in the GI tract
Metabolism: First-pass in liver (higher bioavail injectable)
Side effects: Bone marrow hypoplasia (puppies <11weeks) maybe
Ondansetron
Granisetron
Dolasetron
MOA: serotonin (5-HT3) receptor antagonist - peripherally in the GI tract (vagal afferent input) and centrally (CRTZ and MVC)
Metabolism: Liver (ondansetron); dolasetron metabolized into active form by carbonyl reductase -> eliminated by hepatic P-450 enzymes; eliminated in urine/bile
Side Effects: constipation, diarrhea, somnolence, prolongation of QT interval, potential emesis at higher doses
Metoclopramide
MOA: Antidopaminergic activity, blocks 5-HT3 receptors (potent blocker of CRTZ). Increases sensitivity of smooth muscle in the SI to ACh (prokinetic effect)
Met: Kidneys
SE: Extrapyramidal signs can be seen with overdose (behavioral changes, apparent hallucinations), lower dose needed if substantial decrease in GFR. Less effective in cats
Promazine derivatives (chlorpromazine, prochlorperazine, acepromazine)
MOA: antidopaminergic and antihistamine effects that blocks the CRTZ and at high doses, the MVC. Also has anticholinergic, antispasmodic and a-adrenergic blocking effects
Met: Liver
SE: Vasodilation and hypotension, sedation, increased CVP, bradycardia/tachycardia, antiarrhythmic qualities, CNS signs if hepatic insufficiency present
Anticholinergic drugs (aminopentamide)
MOA: blocks the cholinergic receptors in the brain (MVC) and upper GI tract via the vagus nerve (specific receptors unknown)
Met: liver, excreted by kidneys
SE: Caution with glaucoma, cardiomyopathy, tachyarrhythmias, hypertension, MG or GE reflux. Less effective than other antiemetics, constipation, vomiting, ataxia, confusion/behavioral changes, urinary retention, mydriasis, tachycardia, allergic reactions
Cisapride
MOA: 5-HT4 serotonergic agonists - enhances gastric emptying, increased GE sphincter pressure, increases SI and colonic motility (no effect on striated mm)
Met: First-pass liver; only 30% bioavail in cats
SE: Cardiac conduction effects (prolonged QT), vomiting, diarrhea, GI discomfort, drooling, agitation
Bethanechol, ranitidine, nizatidine
MOA: cholinomimetic; bethanechol binds to muscarinic receptors; ranitidine/nizatidine inhibits acetylcholinesterase
SE: Beth affects motility throughout GI tract; -itidine drugs promote gastric emptying
Erythromycin
MOA: Motilin receptor agonist- increases lower esophageal sphincter tone, promotes SI/colonic peristalsis. Enhances gastric contractions, improvement of the lower esophageal sphincter
Met: Liver
SE: Tolerance with sustained use, vomiting, diarrhea, abdominal pain, allergic reaction, hepatotoxicity, cholestatic jaundice, QT prolongation, tachycardia, ototoxicity, superinfection
Misoprostal
MOA: synthetic prostaglandin E1 analog - increases gastric contractions, enhances small bowel motility, promotes gastric emptying
Met: Liver (active form misoprostol acid), excreted in urine
SE: Diarrhea, abdominal cramping, vomiting, flatulence, headache, uterine contractions, allergic reaction
Cimetidine
MOA: H2-receptor antagonist
SE: Potent inhibitor of hepatic P-450 enzymes; can affect metabolism of toxins or other drugs, decreases hepatic blood flow
Ranitidine
MOA: H2-receptor antagonist
SE: Vomiting, diarrhea, abdominal pain, dizziness, blood dyscrasias, renal dysfunction
Famotidine
MOA: H2-receptor antagonist
Longest acting and most potent of the H2s
SE: vomiting, diarrhea, reduced appetite, allergic reaction, leukopenia, thrombocytopenia, hepatotoxicity, renal dysfunction, injection site reactions
Nizatidine
MOA: H2-receptor antagonist
SE: Exclusively eliminated through kidneys
Omeprazole
MOA: PPI
SE: inhibits hepatic P-450 enzymes, may cause elevations in liver enzymes, diarrhea
Esomeprazole
MOA: PPI
