GI: Antiemetics Flashcards
Most notable signs of vomiting
Nausea (drooling) and abdominal heaving (retching)
Signals for vomiting
Periphery: irritation, hypertonicity, distention
Central: CRTZ and vestibular apparatus
4 areas in the brain
Vomiting center
Chemoreceptor trigger zone (CRTZ)
Solitary tract nucleus
Vestibular apparatus
T/F: You must block one or more of the receptors for successful therapy
TRUE
Emetic agents
Apomorphine
Ipecac syrup
Xylazine
Apomorphine
Opiate that doesn’t stimulate opioid receptors
Used in dogs, too much excitement for cats
Dopamine (D2) receptor agonist
Ipecac syrup
Peripheral and and central
Gastric lavage after 2nd dose
Cardiotoxicity in cats
Serotonine (5-HT3)
Xylazine
Used in cats
a2 adrenergic receptor
Classes of antiemetics
Metoclopramide
NK1 receptor antagonist
Serotonine antagonists
Antihistamines (H1R antagonists)
Phenothiazines
Antimuscarinics
Others (cannabinoids, glucocorticoids)
Metoclopramide MOA
Low dose: Inhibits D2
High dose: inhibits 5-HT3 receptors at CRTZ or vagal afferent neurons
↑ emptying of stomach and upper duodenum
Metoclopramide uses
Nausea, vomiting and esophageal reflux ( cancer therapy)
Peripheral causes (ulcers, motility)
Prokinetic: ↑ gastric emptying
Metoclopramide adverse effects
↑ Gi discomfort @ high doses
Sedation and extrapyramidal effect
Metoclopramide precaution
Don’t use with monoamine oxidase inhibitors selegiline or preventic (amitraz collars)
GI obstruction
Maropitant (cerenia)- NK1 receptor antagonist
Approved in dogs and cats
Selective antagonist of substance P @ NK1 receptor in CRTZ and vomiting center
Ondansetron (Zofran) - Serotonin 5HT3 antagonist
Effective in nausea and vomiting
Most potent
Side effects: dizziness and constipation
Weak Serotonin 5HT3 antagonists
Cisapride, renzapride, metoclopramide
Galanolactone- Serotonin 5HT3 antagonist
Diterpenoid found in ginger
Partially mediates anti-emetic activity of plant
Meclizine- antihistamines
Diphenhydramine (benadryl), dimenhydrinate, and promethazine
Works on vestibular apparatus and CRTZ
Most prominent in dogs and cats
Meclizine side affect
Sedation (H1 receptors involved in sleep, wake cycle)
Phenothiazine tranquilizers
Chlorpromazine, prochlorperazine, acepromazine
Phenothiazine tranquilizers MOA
Low dose: anti-dopamine at CRTZ
Antihistaminergic effect @ CRTZ
High dose: anticholinergic effect @ vomiting center and periphery
Phenothiazine tranquilizers adverse effects
Sedation, extrapyramidal signs, hypotension
Cannabinoids
THC and dronabinol (marinol)
Useful when others don’t work
↑ appetite in cats
