Anti Emetics

Question 1

D2 antagonists (Chemical trigger zone)

Answer 1

Chlorpromazine, acepromazine - not specific, h1 and MACh too.
Side effects: sedation, hypotension, platelet dysfunction - NOT IN PREGNANCY

Metoclopramide - blocks 5HT3 too and inc tone in LES
Side effects: movement disorders and menstrual disorders (prolactin release)

Question 2

5HT3 antagonists - chemical trigger zone and visceral afferents

Answer 2

Ondansetron, nabilone (cannabinoid) for chemo or cytotoxic induced
Side effects: drowsiness and euphoria

Cisapride (5ht4) - withdrawn, long QT, inc motility and les contraction
Side effects: cramps and diarrhoea

Corticosteroids e.g. dexamethasone - Dec pg activity, inc endorphins, potentiate other antiemetics

Question 3

H1 antagonists (vestibular nuclei and NTS) - not for chemo induced as not CTZ

Answer 3

Diphenhydramine, cyclizine, promethazine (morning sickness)
Central action - motion sickness plus anti muscarinic
Side effects: sedation

Question 4

MACh blockers (vestibular nuclei and NTS) - motion sickness

Answer 4

Hyoscine, scopolamine

Anti muscarinic effects eg drowsiness, blurred vision, dry mouth