Anti-emetics Flashcards
Classes of anti-emetics
Corticosteroids, serotonin 5-HT3 antagonist, Neurokinin-R antagoinst, Dopamine-R antagonist, anticholinergics, antihistamine/anticholinergic, antipsychotics, benzodiazepine
Corticosteriods
Dexamethasone
MoA of corticosteroids
Basis of anti-emetic effect unknown
Used with 5-HT3 antagonist for acute & delayed CINV
SE of corticosteroids
Unlikely with short-term use.
Long term use (>2w) –> iatrogenic Cushing’s syndrome (rounded face, muscle wasting, easy bruising, immunosuppression)
5-HT3 antagonist
Ondansetron (1G), Palonosetron (2G)
MoA of 5-HT3 antagonist
Acts on GIT 5-HT3 receptors –> prevents activation of vomiting centre
Use of 5-HT3 antagonist
Use with corticosteroid, NK-R antagonist
Prevents acute CINV not delayed
SE of 5-HT3 antagonist
Generally well-tolerated but may cause h/a, dizziness, constipation
Ondansetron: dose reduction with hepatic insufficiency, small risk of arrhythmia
CYP450 metabolism — clearance may be affected
Neurokinin receptor antagonist
Aprepitant (use with CS, 5-HT3 antagonist for acute AND delayed CINV)
MoA of NK-R antagonist
Act on NK-1 receptor in area postrema of CTZ
SE of NK-R antagonist
Fatigue, dizziness, diarrhoea
CYP3A4 metabolism —can be affected by inhibitors such as verapamil, ritonavir
Dopamine receptor antagonist
Metoclopramide
MoA of Dopa-R antagonist
D2 receptor antagonism blocks CTZ from detecting toxins –> Decreased N&V
SE of Dopa-R antagonist
Extrapyramidal SE: restlessness, Parkinsonian Sx especially in elderly
LT use can cause irreversible tardive dyskinesia
Elevated prolactin levels (gynaecomastia, galactorrhoea)
Anticholinergics
Hyoscine/Scopolamine
MoA of anticholinergics
Act on vestibular system and vomiting centre
Use of anticholinergics
PREVENT motion sickness
SE of anticholinergics
Typical anticholinergic effect such as urinary retention, dry mouth, BoV
SE can be reduced by transdermal patch than oral
Mixed H1 antihistamine, anticholinergic
Diphenhydramine
MoA of antihistamine/anticholinergic
H1 and M1 receptor antagonism –> acts on vestibular system and vomiting centre to stop motion sickness
Use of antihistamine/anticholinergic
TREAT motion sickness
Due to sedative effect of antihistamine, useful for CINV
SE of antihistamine/anticholinergic
Sedation (antihistamine component), anticholinergic effects
Antipsychotics
Prochlorperazine (D/Musc/H anta), Droperidol (D/weak H), olanzapine
Use of olanzapine
For delayed CINV
MoA of antipsychotics
D2 receptor antagonism @ CTZ
Musc antagonism @ vestibular system, vomiting centre
Weak H1 antagonism
SE of antipsychotics
Sedation, EPSE (less with olanzapine), prolonged QT interval (Droperidol)
Benzodiazepines
Lorazepam, diazepam
MoA of BZD
Bind to allosteric site of GABA receptor –> Cl conductance, potentiate GABA action
SE of BZD
Sedation, respiratory depression if OD
Contraindication of BZD
Pregnancy (especially 1st trimester due to increased risk of cleft palate)
