anitemetics Flashcards
name some d2r antagonists used for antiemetics
metoclopramide
domperidone
how to metoclopramide and domperidone work
- d2r = main receptor in chremoreceptor trigger zone
- so these drugs block n and v caused by trigger zone
- also d2 in the gut is normally a relaxant so antagonising it = prokinetic effect
SE domperidone and meotclopramide
- diarrhoea
- metoclop = EPS - stm = acute dystonic reaction e.g. oculogyric crisis
- dom = doesnt cross BBB so no EPS. but risk of QT-I prolonged
how long should you prescribe metoclopramide for in
- no more than 5 days due to EPS risk
CI to meto and dom
do not
- Neonates
- cardiac conduction defects
- intestinal perforation
relative
- children
- young adults
- hepatic impairment thats severe
- intestinal obstruction
- parkinsons
interactions of domperidone
- drugs prolonging QTI, cyp450-i
starting dose of meto and dom
10mg 8hrly
how else can you give meto
IM or IV at same dose
how to give IV meto
- slowly; over at least 3 mins for 10mg
name some H1r antagonists used as antiemetics
cyclizine
cinnarizine
promethazine
indications for h1r antagonist antiemetics
- prophylaxis of N and V esp in motion sickness or vertigo
MOA of H1r antagonists that are used for antiemetics
- h1 and muscarinic receptors are key in vomiting centre in the medulla (this is different to the chemoreceptor trigger zone) and key for communication with vestibular system.
- cyclizine blocks both receptors
SE H1r antagonists as antiemetics
drowsiness
- cyclizine is least sedating drug
- dry throat and dry mouth
- post IV injection - transient tachycardia - palpitations
avoid h1r antagonists antiemetics in which patients
- hepatic encephaloapthy
- prostatic enlargement or those at risk of anticholinergic SE
interactions with H1r antagonists antiemetics
- other sedatory drugs
- increase the effect of ipratropium or tiotropium
