Ondansetron
2,3-dihydro-9-methyl- 3-[(2-methylimidazol-1-yl)methyl] carbazol-4(1H)-one
CAS number 99614-02-5	ATC code A04AA01
Chemical formula	CH19N3O
Molecular weight	325.9
Bioavailability	~60%
Metabolism	hepatic
Elimination half-life	4.1-11.6 hours (oral) 2.5-6.1(IV)
Excretion	renal
Pregnancy category	B1 (Australia)
Legal status	Schedule 4 (Australia) PoM (UK)
Delivery	tablets, wafers, suppositories, syrup, injection (IV/IM)

Ondansetron is a 5-HT₃ receptor antagonist principally used as an antiemetic. It is currently marketed by GlaxoSmithKline under the trade name Zofran.

Although highly effective, its high cost limits its use to controlling postoperative nausea and vomiting (PONV) and chemotherapy-induced nausea and vomiting (CINV). It is also used off-label to treat hyperemesis gravidarum in pregnant women.

See also

• Granisetron
• Dolasetron
• Alosetron (not an antiemetic but another 5-HT₃ antagonist investigated for controlling irritable bowel syndrome)