Ondansetron

Metoclopramide

Antiemetic

Anesthesia

Nausea

Adverse effect

Prochlorperazine

Vomiting

Pharmacology

Aprepitant

Medicine

Australian Prescriber

Antiemetic drugs: what to prescribe and when SUMMARY Nausea and vomiting are common symptoms with many possible causes, including the adverse effects of drugs.If a drug is indicated, the cause guides the choice of antiemetic drug.The main antiemetic classes include antagonists of the serotonin, dopamine, histamine, muscarinic and neurokinin systems, corticosteroids and benzodiazepines.Some antiemetics appear more effective for specific indications.Serotonin and neurokinin antagonists, such as ondansetron and aprepitant, are highly effective in treating chemotherapy-induced nausea and vomiting.Metoclopramide and antihistamines are first-line options for nausea and vomiting in pregnancy.Serotonin antagonists and some dopamine antagonists, such as metoclopramide, can prolong the QT interval on the ECG.Dopamine antagonists can cause extrapyramidal adverse effects, particularly in children. GastroenteritisAcute gastroenteritis is caused by viral, bacterial or protozoal infections.Therapeutic options available for adults with vomiting secondary to gastroenteritis include dopamine antagonists such as metoclopramide or prochlorperazine and serotonin antagonists such as ondansetron. 15usea and vomiting resulting from acute gastroenteritis is particularly challenging in children.Until the early 2000s, antiemetics including promethazine, metoclopramide and prochlorperazine were widely used in children, however their use is now controversial due to reports of adverse events including sedation and extrapyramidal reactions. 16en an antiemetic drug is indicated, serotonin antagonists such as ondansetron are now recommended in guidelines, such as those published by the Royal Children's Hospital Melbourne. 17These guidelines recommend a single weight-based dose of oral ondansetron.Children weighing 8-15 kg should receive 2 mg, children weighing 15-30 kg should receive 4 mg and children weighing more than 30 kg should receive 8 mg.Ondansetron is not recommended in children under six months of age or less than 8 kg in weight. 17A systematic review reported that oral ondansetron reduced vomiting, hospitalisation and the need for intravenous rehydration in children with acute gastroenteritis. 18Intravenous ondansetron or metoclopramide also reduced vomiting and hospitalisation.A single study in the review reported that rectal dimenhydrinate was effective at reducing vomiting.

Antiemetic drugs: what to prescribe and when