Anti Emetics Flashcards
(34 cards)
What is emesis
Forceful evacuation of gastric contents
Protective physiological mechanism when something harmful is ingested
What region is referred to as the brain stem emetic control centre or the dorsal vagal complex
Brain stem in a neural network on the dorsal surface of the medulla oblongata
What are the three major inputs to the dorsal vagal complex causing vomiting?
Chemoreceptor
Vagal pathway
Vestibular pathway
Chemoreceptor trigger zone in emesis
Endogenous substances, toxins, drugs
Vagal pathway in emesis
Sensory input (pain, smell, sight, thought)
Stimuli from pharynx
Stimuli from gi tract
Vestibular pathway in emesis
Disorientating motion
The therapeutic approach to emesis involves…
Blocking the neurotransmitters involved in triggering the response
Describe the receptor pharmacology of emesis
Vomiting centre - muscarinic, histamine, neurokinin, serotonin
Vestibular pathway- histamine, muscarinic
Vagal - serotonin
Chemoreceptor- dopamine, neurokinin, serotonin
Chemoreceptor trigger zone receptors
Dopamine (d2)
Substance p/ neurokinin (NK)
Serotonin (5HT3)
Vagal pathway receptors (emesis)
Serotonin (5HT3)
Vestibular pathway receptors (emesis)
Histamine (H2)
Muscarinic (M)
Cyclizine
Anti emetic histamine receptor antagonist
Motion sickness
SE:drowsiness or sedation
Cinnarizine
Anti emetic histamine receptor antagonist
Motion wickedness, vestibular disorders eg Ménière’s disease, vertigo
SE: drowsiness, sedation
Promethazine
Anti emetic histamine receptor antagonist
Severe morning sickness in pregnancy
SE: drowsiness, sedation
Betahistine hydrochloride (sero)
Activates H receptors on blood vessels in the inner ear
Local vasodilation
Increased permeability
Reverses problem of endolymphatic hydrops
SE: gi, headache, rash, pruritus
Phenothiazines
Anti emetic dopamine receptor antagonist
Severe morning sickness
Oral, iv, suppository
Inexpensive
SE: sedative, hypotension, dystonia, dyskinesia
Perphenazine
Anti emetic dopamine receptor antagonist
SE: gi, opioid induces emesis, viral gastroenteritis, uraemia.
Prochloropromazine
Anti emetic dopamine receptor antagonist
SE: gi, uraemia, viral gastroenteritis, opioid induces emesis
Metoclopramide
Anti emetic dopamine receptor antagonist
Penetrates blood brain barrier, increases gi motility
SE: movement disorders, fatigue, motor restlessness
Domperidone
Motillium
Anti emetic dopamine receptor antagonist
Does not cross BBB.
Used for migrane and cytotoxic therapy induced emesis. Emergency contraception emesis too.
Oral/ iv/ suppository
Anti emetic dopamine receptor antagonists have a….
Powerful anti emetic action.
Will antagonise muscarinic and histamine receptors too.
Hyoscine
Anti emetic muscarinic receptor antagonist
Non selective
Motion sickness
Oral /patch
SE: dry mouth, blurred vision. Less sedative effects than anti histamines
Ondansetron
Anti emetic serotonin receptor antagonist
Drug choice for CINV (chemotherapy) PONV (anaesthetics)
Oral, suppositories, iv, Im,
SE: gi, headaches
Granisetron
Anti emetic serotonin receptor antagonist
Oral, iv.
SE; gi, headaches
