GI drugs 2 Flashcards
(37 cards)
categories of prokinetics
- Dopamine Antagonists
- Metoclopramide
- Domperidone - Serotonin Receptor Modulators
- Cisapride - Miscellaneous agents
- H2-receptor antagonists
- Cholinergics
types of dopamine antagonists used as prokinetics?
- Metoclopramide (Maxeran®)
- Domperidone (Motilium®)
how does metoclopramide work as a prokinetic? mechanism of action? where does it act?
- Acts peripherally as a prokinetic to increase ACh
> activates prejunctional 5-HT4 (serotonin) receptors on enteric cholinergic nerves
> blocks inhibitory dopamine (D2) receptors on enteric cholinergic nerves - Effects are limited to upper GI tract; however, not well-established
> Increase lower esophageal sphincter and promote gastric emptying; less effect on the distal bowel
what animals is metoclopramide used in? what animal should we exhibit caution with and why?
- Used in horses; dogs and cats
- Caution: horses–behavioural (excitement) changes
what forms does metoclopramide come in?
Tablets, oral solution, injectable
difference between domperidone and metoclopramide?
Domperidone is similar to metoclopramide; does not cross BBB as readily;
Serotonin Receptor Modulator used as a prokinetic
Cisapride
how does Cisapride work? availability and adverse effects? what applications and species is it used for?
- Acts peripherally to stimulate 5-HT4 receptors on presynaptic enteric neurons promoting the release of ACh
- Withdrawn from market due to adverse cardiac effects in humans
> Can be obtained as a compounded product from pharmacies - Broadest spectrum prokinetic
> Gastric reflux, gastroparesis (delayed emptying)
> Ileus; dog, cat, horse
> Constipation and megacolon in cats
How do H2-receptor antagonists work as prokinetics?
Nizatidine (Axid®) and Ranitidine (Zantac®)
- Appear to inhibit acetylcholinesterase which increases ACh levels promoting GI motility throughout the stomach, SI and colon
- Reduction in HCl production also stimulates stomach motility promoting emptying
what are two H2-receptor antagonists that are used as prokinetics
Nizatidine (Axid®) and Ranitidine (Zantac®)
what cholinergic is used as a prokinetic? is it commonly used and why?
- Bethanechol (Urecholine®, generic, compounded)
- Use is limited by adverse effects
> Salivation, abd cramps, diarrhea, bradycardia
adverse effects of bethanechol
Salivation, abd cramps, diarrhea, bradycardia
how does bethanechol work as a prokinetic?
Promotes contractility throughout GI tract
species and possible application for bethanechol use as a prokinetic?
- Cats, dogs, cattle? horses?
- May be of benefit in canine idiopathic megaesophagus
Diarrhea can result from an imbalance with:
- motility (hyper or hypo)
- water and electrolyte secretion
most treatments for diarreah use what strategy?
Most treatment is symptomatic and does not address the underlying problem
- replace fluids
- replace electrolytes and maintain acid/base balance
- provide relief
how can diarreah be a defence mechanism?
- eliminate pathogens
- eliminate toxins
categories of antidiarrheals
- Adsorbents
- Antimotility
- Antisecretory
how do adsorbents work?
Adsorbents bind chemicals, toxins preventing their absorption
- bound agents are eliminated in feces
- adsorbents can bind other drugs interactions
- many adsorbents also have protectant effects
> bind and coat mucosal surface
adsorbents used as antidiarrheals
- Bismuth Subsalicylate (Pepto-Bismol®)
- Kaolin/Pectin (Kaopectate®)
when is Bismuth Subsalicylate (Pepto-Bismol®) used? how does it work? adverse effects?
- used in acute diarrheas; may darken stool !
- chronic use can yield constipation
- bismuth, like sucralfate, acts as a protectant and coats the mucosa
- salicylate component inhibits PG’s yielding an anti-inflammatory effect
> caution due to salicylate component, which is absorbed in dogs and cats; unlikely in standard dosages to produce toxicity
> however, use in cats probably should be cautious or avoided
how do Kaolin/Pectin (Kaopectate®) work as antidiarrheals? efficacy? should be careful with what formulations? what product versions are available?
- adsorbents
- Kaolin (attapulgite or aluminum silicate) and pectin (carbohydrate)
- Supposedly binds toxins, bacteria….and other drugs
> Efficacy is questionable for binding toxins
Does not appear to reduce electrolyte and fluid loss
- Careful with salicylate containing formulations
- Veterinary products can be kaolin and pectin only, or contain other anti-
diarrhea drugs and compounds
Antimotility & Antisecretory drug categories for antidiarrheals
- Opioids
- Anticholinergics
types of opioids that are used as antidiarrheals
- Loperamide (Imodium®)
- Diphenoxylate (Lomotil®)
