anti emetics Flashcards
how and where is emesis controlled?
controlled and centralised by brainstem in a nautral network on dorsal surface of medulla - referred to as the “brainstem emetic control centre” or dorsal vagal complex
what is the vomiting reflex regulated by?
CNS (medulla)
what is the main site of action for ant-emetic drugs?
chemoreceptor triggering zone (CTZ)
what is the CTZ physically associated with?
emetic centre
which side of the blood brain barrier is CTZ located?
blood side
what is the target for anti-emetic drugs?
blockade of neurotransmitters involved in triggering emesis
name the 6 endogenous neurotransmitters involved in triggering emesis
serotonin AcH Dopamine Substance P Histamine Enkephalin
name the various pathways involved in stimulating the vomiting centre
vestibular pathway
vagal pathway
CTZ and emetic centre
what stimulates the vestibular pathway?
disorientating movement
what stimulates the vagal pathway?
sensory input (pain, smell, sight, thought)
stimuli from pharynx
stimuli from GI tract
what stimulates the CTZ and emetic centre?
endogenous substances
toxins
drugs
name 7 classes of anti emetics
H1 histamine antagonists muscarinic receptor antagonists D2 Dopamine antagonists 5HT3 serotonin antagonists NK1R neurokinin -1 antagonists cannabinoids corticosteriods
name 3 H1 (histamine) antagonists
cyclizine
cinnarizine
promethazine
what is the mechanism of action of H1 (histamine) antagonists and in which areas to they act ?
blocks H1 (histamine) receptors on vestibular pathway and vomiting centre
what are type of emesis are H1 (histamine) antagonists used to treat?
cyclizine - motion sickness
cinnarizine - motion / vestibular disorders
promethazine - severe morning sickness
what are the side effects of H1 (histamine) antagonists?
drowsiness
sedation (contributes to efficacy)
name 2 muscarinic receptor agonists used as anti-emetics
hyoscine
scopolaine
what is the mechanism of action of muscarinic receptor agonists and in which areas to they act ?
block muscarinic receptors in vestibular pathway and vomiting centre
block neurotransmitter Ach
what are type of emesis are muscarinic receptor antagonists used to treat?
general purpose motion sickness (drug of choice)
what are the side effects of muscarinic receptor antagonists?
dry mouth
blurred vision
less sedation (than antihistamines)
name 5 dopamine antagonists
phenothiazides prochlorpromine perphenazine metaclopromide domperidone
what is the mechanism of action of dopamine anatagonists?
block dopamine receptors - strong representation in CTZ
also antagonise M and H receptors
what type of emesis are phenothiazides, prochlorpromine and perphenazine used to treat?
uremia opiod induced emesis CINV GI disorders viral gastro enteritis
what are the side effects of phenothiazides, prochlorpromine and perphenazine?
sedative
hypotension
dystonia
dykinesia
which body system does metaclopromide act on?
GIT, increase GI motility
what are the side effects of metaclopromide?
movement disorders
fatigue
motor restlessness etc.
penetrates BBB
what is domperidone used to treat?
migraine
cytotoxic induced therapy emesis
emergency contraceptive sickness
does not penetrate BBB - few SE
name four 5HT3 serotonin antagonists
ondanstron
granistron
palonosetron
tropisetron
what is the mechanism of action for 5HT3 serotonin antagonists?
blocks serotonin receptors in CTZ, vomiting centre and vagal pathway
what is the drug of choice for CINV and PONV?
ondanstron
what are the side effects of 5HT3 serotonin antagonists?
GI disterbances
headache
name three NK1R neurokinin-1 antagonists?
aprepitant fos aprepitant (PRODRUG) maprepitant
what is the mechanism of action for NK1R neurokinin-1 antagonists?
antagonists substance P
what is NK1R neurokinin-1 antagonists used for?
CINV and PONV
what are the side effects of NK1R neurokinin-1 antagonists?
fatigue listlessness constipation/ diahorrea loss of appetite hiccups
name 2 cannabinoids
nabilone
marinol
what is the mechanism of act of cannabinoids?
agonist cannabinoid receptors
act via opioid receptors in CTZ
what are cannabinoids used to treat?
CINV
what are the side effects of cannabinoids?
drowsiness dizziness dry mouth mood changes postural hypotension
which corticosteroid is used as an anti-emetic and which type of emesis is it used for?
dexamethosone
cytotoxic drugs - used in combo with D2 or 5HT3 antagonist for improved action
