Ondansetron
Sold as Zofran
Ondansetron blocks serotonin (5-HT3) receptors in the gut and brain to prevent nausea and vomiting. Originally approved for chemotherapy- and surgery-related nausea, it's also widely prescribed off-label for nausea in pregnancy.
What it treats
Prevents nausea and vomiting from chemotherapy, radiation, and surgery. Also used off-label for hyperemesis gravidarum / morning sickness in pregnancy.
Typical dosing
Typical adult dose: 4–8 mg by mouth every 8 hours as needed, or as directed by your prescriber.
Side effects
Common: headache, constipation, tiredness. Serious (rare): QT prolongation (irregular heartbeat), serotonin syndrome when combined with other serotonergic drugs.
Interactions to know
Caution with other drugs that prolong the QT interval, and with other serotonergic medications (e.g. SSRIs, tramadol) due to serotonin syndrome risk.
Pregnancy & breastfeeding
FDA Pregnancy Category B. Widely used off-label for nausea in pregnancy. Some studies suggested a small association with cleft palate in the first trimester; larger studies have not confirmed increased birth defect risk. Discuss with your OB or midwife before use — do not self-prescribe.
Clinical content reviewed by the BetterBuyRx clinical team.
Educational only. Not medical advice. Always confirm with your prescriber or pharmacist.