Anti emetic drugs

on 23.12.09 with 1 comment

• For motion sickness
• H1 antagonist (classical)
• Used as a sedative in children (it is a very safe sedative)
• Also has antimuscarinic actions
• It is very effective at preventing motion sickness (since the vestibular afferents input in the vomiting center which has H1 and Muscarinic receptors
• Not used for the driver because is makes them drowsy
• Hyocine (scopolamine)
• Muscarinic antagonist (M2)
• Used as a patch behind the ear
• For CTZ mediated vomiting
• A phenothiazine
• A D2 antagonist
• Has no antipsychotic effects
• It is useful as an antiemetic as well as for dizziness
• Has minor anticholinergic effects (it may work in motion sickness, however, the above  drugs are preferred)
• Since it blocks D2 receptors elsewhere (e.g. substantia nigra), it will cause
extrapyramidal effects
Chlorpromazine, another phenothiazine, can also be used as an antiemetic, although it tends to be very sedative. It also has antipsychotic effects
• A D2 antagonist
• Also a weak 5HT3 antagonist
• Increases the motility of the gut in the upper regions (hence it does not cause diarrhoea -
only facilitates gastric emptying)
• This is useful because when someone is nauseous, there is often gastric stasis, which means that drugs given by the oral route will not be absorbed effectively. Also, the drugs should not be given when the person is about to vomit, otherwise they will just vomit up the drug.
• Metaclopromide will help the absorption of drugs because it stimulates gastric
• For vomiting associated with vagal afferents (gut disorders, heart, testes, gut irritants - all stimulate the 5HT3 receptor on the vagal afferents)
• A 5HT3 antagonist
• Excellent antiemetic
• It is very effective in patients receiving cancer chemotherapy (radiation or cisplatin - both
of which stimulate the release of serotonin in the gut)
• Can also be used for CTZ nausea (though its main used is in conjunction with anti cancer drugs)

Category: Medical Subject Notes , Pharmacology Notes



gh said...
May 6, 2010 at 9:39 PM

what about doxylamine and pyridoxine in morning sickness ??

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