8.3 Anti-emetics Flashcards
(33 cards)
What is Emesis and give a definition
Give two potential stimuli
Emesis = vomiting
It is a physiologic response to irritating and potentially harmful substances in blood or gut
May be due to excessive vestibular stimulation or psychological stimuli
Emesis involves co-ordination of _______, _______, _______contractions controlled by the vomiting center
pharyngeal,GI, abdominal wall
Where is the vomiting centre located
In the medulla
Give some examples of centres which influence the vomiting centre
Which have positive/negative effects?
Most are positive influences from gut, vestibular apparatus, solitary tract and chemoreceptor trigger zone (CTZ)
Cerebral cortex can be positive or negative
Give examples of receptor found in the following:
- Chemoreceptor Trigger Zone (CTZ)
- Solitary Tract
- Gut
- Vestibular Apparatus
Chemoreceptor Trigger Zone (CTZ): D2, M1, 5-HT3
Solitary Tract: D2, M1, 5-HT3, H1, NK1
Gut: 5-HT3
Vestibular Apparatus: M1, H1
Give the 6 classes of Anti-Emetics
- dopamineinhibitors
- serotonininhibitors
- anti-histamines
- phenothiazine
- anti-cholinergics
- neurokinin-1 inhibitors
Give 2 examples of dopamine Inhibitors + where each acts
metoclopramide and domperidone
Give the MoA of dopamine inhibitors
Binds to receptors to inhibit action of dopamine
CTZ = rich in D2 receptors
Prokinetic effect in GI
Give 2 side effects of dopamine inhibitors and explain why each occurs
Diarrhoea: b/c it is prokinetic
Extrapyramidal side effects because of its dopaminergic effect (normally metoclopramide)
Give 2 contraindications of dopamine inhibitors
Obstruction
Perforation
Give an example of a serotonin Inhibitor + where it acts
ondansetron
Give the MoA of serotonin inhibitors
Binds to receptors to inhibit action of serotonin
CTZ – rich in 5-HT3 receptors
Serotonin released by gut in response to emetogenic stimuli
Give 3 side effects of serotonin inhibitors and explain why each occurs
Constipation, Diarrhoea, Headache
Give a contraindication of serotonin inhibitors and when it should be completly avoided
Risk of QT prolongation
Avoid with SSRI, antipsychotics, quinine
Give 2 examples of Anti-histamines + where they act
cyclizine and promethazine
Give the MoA of Anti-histamines
Blocks H1, M1 receptors between vestibular system, vomiting center
Give 2 side effects of Anti-histamines
Drowsiness and Anti-cholinergic effects
Give 2 contraindications of Anti-histamines
Prostatic hypertrophy
Hepatic encephalopathy
Give 2 examples of phenothiazines
prochlorperazine and chlorpromazine
Give the MoA of Phenothiazines
Blocks D2 receptor in CTZ, gut and to a lesser extent, blocks H1, M1 receptors in CTZ, vestibular apparatus
Give 4 side effects of Phenothiazines
Drowsiness, postural hypotension, extrapyramidal side effects, anti-cholinergic side effects
What is the biggest risk with Phenothiazine and therfore when should you avoid it?
Risk of QT prolongation
Avoid with quinine, SSRIs, anti- psychotics
Give an example of a Anti-cholinergic
hyoscine hydrobromide
Give the MoA of Anti-cholinergics
Blocks M1 receptors
