pharmacology of intestinal motility secretion, nausea and vomiting Flashcards
what is vomiting
a defence mechanism triggered by the vomiting/emetic centre located in the brain stem
what may cause nausea and vomiting
anxiety motion sickness migraine pregnancy side effects of drugs
what are the main neurotransmitter systems involved in nausea and vomiting
5-HT
dopamine
ACh
what are the three main antiemetic drugs
> anti-histamines (H1 receptor antagonists)
antimuscarinics (muscarinic ACh receptor antagonists)
5-HT3 receptor antagonists
dopamine receptor antagonists
neurokinin-1 receptor antagonists
examples of antihistamines
cyclizine
promethazine
diphenhydramine
examples of antimuscarinics
scopolamine (hyoscine)
examples of 5-HT3 receptor antagonists
ondansetron
granisetron
palonosetron
examples of dopamine receptor antagonists
chlorpromazine droperidol haloperidol prochlorperazine metoclopramide
examples neurokinin-1 receptor antagonists
fosaprepitant
apreptant
action of antihistamines
> act primarily as antagonists at histamine H1 receptors in the brain
indications for antihistamines
indicated for nausea, vomitting > motion sickness
side effects of antihistamines
sedation lol
action of antimuscarinics
they act primarily as antagonists at muscarinic acetylcholine M1 receptors in the brain
indications for antimuscarinics
motion sickness
side effects of antimuscarinics
dry mouth
tachycardia
constipation
action of 5-HT3 receptor antagonists
they act primarily as antagonists at 5-HT3 receptors in the chemoreceptor trigger tone of the medulla in the hindbrain
>also the 5-HT3 receptors in the GI tract
side effects of 5-HT3 receptors antagonists
constipation
diarrhoea
headache
action of dopamine receptor antagonists
they act primarily as antagonists at D2 receptors in the chemoreceptor trigger zone of the medulla in the hindbrain
>also D 2 receptors on the GI tract
side effects of D2 receptor antagonists
diarrhoea and extrapyramidal side effects
neurokinin-1 receptor antagonists mode of action
act as antagonists at NK1 receptors in the GI tract in the hindbrain blocking the effects of substance P
side effects of Neurokinin-1 receptor antagonists
constipation and headache
what are drugs that affect GI motility
antidiarrhoeal drugs
laxatives
what are antidiarrhoeals
> they are electrolyte replacements
loperamide and diphenoxylate are opiates that has reduced effect on the brain
they are sometimes combines with atropine
high doses of loperamide have been associated with drug abuse
side effects include = constipation sedation respiratory depression
what are laxatives
> ispaghula husk = bulk forming laxative
lactose = osmotic laxative (hepatic)
senna-stimulant purgative = increases electrolyte/water secretion
