Ondansetron, sold under the brand name Zofran among others, is a medication used to prevent nausea and vomiting caused by cancer chemotherapy, radiation therapy, or surgery. It is also effective for treating gastroenteritis. It can be given by mouth or by injection into a muscle or into a vein.Common side effects include diarrhea, constipation, headache, sleepiness, and itchiness. Serious side effects include QT prolongation and severe allergic reaction. It appears to be safe during pregnancy but has not been well studied in this group. It is a serotonin 5-HT3 receptor antagonist. It does not have any effect on dopamine receptors or muscarinic receptors.Ondansetron was patented in 1984 and approved for medical use in 1990. It is on the World Health Organizations List of Essential Medicines. It is available as a generic medication. In 2019, it was the 60th most commonly prescribed medication in the United States, with more than 11 million prescriptions. Medical uses
Although an effective antiemetic agent, the high cost of brand-name ondansetron initially limited its use to controlling postoperative nausea and vomiting and chemotherapy-induced nausea and vomiting. Cancer treatment
The 5-HT3 receptor antagonists are the primary medications used to treat and prevent chemotherapy-induced nausea and vomiting and radiotherapy-induced nausea and vomiting. Postoperative
A number of medications including ondansetron appear to be effective in controlling postoperative nausea and vomiting. It is more effective than metoclopramide, and less sedating than cyclizine or droperidol. Pregnancy
Ondansetron is used off-label to treat morning sickness and hyperemesis gravidarum of pregnancy.
It is typically used after other antinausea drugs have failed.There appears to be a low risk of harm to the baby with use during pregnancy, though there may be an increase in heart problems among the babies.Ondansetron is in pregnancy category B in the US. It is not known if ondansetron is excreted in breast milk. Cyclic vomiting syndrome
Ondansetron is one of several antiemetic drugs used during the vomiting phase of cyclic vomiting syndrome. Gastroenteritis
Trials in emergency department settings support the use of ondansetron to reduce vomiting associated with gastroenteritis and dehydration. A retrospective review found it was used commonly for this purpose, being administered in over 58% of cases. Its use reduced hospital admissions, but was also associated with higher rates of return visits to the emergency department. Furthermore, people who had initially received ondansetron were more likely to be admitted on the return visit than people who had not received the drug. However, this effect may simply be due to the agent being used more frequently in people who present with more severe illness. Its use was not found to mask serious diagnoses. Special populations
Children
Ondansetron has rarely been studied in people under 4 years of age. As such, little data is available to guide dosage recommendations. Elderly
It is not necessary to adjust the dosage for people under 75 years of age. The use of ondansetron has not been studied in people older than 75 years of age, and it is not known if dosage should be adjusted for this group.