Anti Emetics Flashcards
What are the three pathways of emesis?
Chemoreceptor trigger zone
Vagal pathway
Vestibular pathway
Where is emesis controlled and centralized?
In the brain stem
What is the chemoreceptors trigger zone related to?
Endogenous substances/toxins/drugs
What is the bagel pathway related to?
Sensory input - pain, smell, sight, thought. Stimuli from the pharynx and stimuli from the GI tract.
What is connected to the vestibular pathway?
Disorientating motion
Which is the main site of action of anti - emetic drugs?
The chemoreceptor trigger zone
Which side of the blood brain barrier is the chemoreceptor zone?
The blood side
Cyclizine, cinnarizine, promethazine are all…
H1 antagonists
When would you use cyclizine?
Motion sickness
When would you use cinnarizine?
Motion sickness and vestibular disorders eg vertigo
When would you use promethazine?
Severe morning sickness
What are some side effects of H1 receptor antagonists?
Drowsiness and sedation
Which pathways do H1 receptor antagonists work on?
All 3
What type of anti emetic is betahistine hydrochloride?
H3 agonist
Describe the mode of action of betahistine hydrochloride
Local vasodilation
Increased permeability
Reverses the underlying problem of endolymphatic hydrops
Hyoscine, scopolaimine
Anti emetic Muscarinic receptor antagonists.
Non selective
General purpose
Motion sickness - drug of choice
Oral and or transdermal patch
Side effects - dry mouth, blurred vision
Less sedative actions than anti histamines
Which pathways do muscarinic receptor antagonists work on?
All 3
Phenothiazinez
Severe morning sickness in pregnancy
Blocks histamine and mAch receptors
Oral, I,v or suppository.
Side effects - sedative, hypotension, dystopia, dyskinesia.
Where do D2 receptors have a strong representation?
In the CTZ
Metoclopramide
D2 receptor antagonist Penetrates bbb Acts on GIT increasing GI mobility Oral, I.v, I.m Side effects - movement disorders (children), fatigue, motor restlessness, spasmodic torticolis, menstruation disorders
Domperidone (motilium)
D2 receptor antagonist
Does not penetrate bbb
Reduced effectiveness but reduced side effects
Migraine and cytotoxic induced emesis, emesis due to emergency hormonal contraception.
Oral, I.v, suppositories.
Which pathways do D2 receptor antagonists work?
Chemoreceptor and vagal
Ondanesetron
5HT3 antagonist
Drug of choice for chemo, anaesthetics, radiation.
Oral, suppositories, I.v, I.m
Side effects - GI disturbances, headache
Where do 5HT3 antagonists work?
Brain stem
Chemoreceptor trigger zone
Vagal pathway
