What is the usual dosing for ondansetron (Zofran) for an adult?

From the Guidelines

The usual dosing for ondansetron in an adult is 8 mg oral twice daily or 8 mg oral dissolving tablet twice daily or three 8 mg oral soluble films or 8 mg or 0.15 mg/kg IV. This dosing is based on the American Society of Clinical Oncology clinical practice guideline update published in the Journal of Clinical Oncology in 2017 1.

Key Points

• The dose of ondansetron can vary depending on the emetic risk category, with high-risk categories such as cisplatin and anthracycline combined with cyclophosphamide requiring more aggressive antiemetic regimens.
• For moderate emetic risk, the recommended dose is 8 mg oral twice daily or 8 mg oral dissolving tablet twice daily or 8 mg oral soluble film twice daily or 8 mg or 0.15 mg/kg IV.
• On subsequent days, the dose can be adjusted to 8 mg oral or IV once daily on days 2-4 or 8 mg oral or IV twice daily on days 2-4.

Administration and Side Effects

• Ondansetron can be administered orally or intravenously, with the oral form available in tablets, dissolving tablets, and soluble films.
• Common side effects of ondansetron include headache, constipation, and dizziness, and patients with liver disease may require lower doses 1.

Special Considerations

• The maximum daily dose of ondansetron should not exceed 24 mg, and patients should be monitored for signs of serotonin syndrome, a rare but potentially life-threatening condition caused by excessive serotonin levels in the body.

From the FDA Drug Label

In a double-blind US trial in 336 patients receiving a cyclophosphamide-based chemotherapy regimen containing either methotrexate or doxorubicin, ondansetron tablets 8 mg administered twice a day, was as effective as ondansetron tablets 8 mg administered 3 times a day in preventing nausea and vomiting A randomized, placebo-controlled, double-blind trial was conducted in the US in 67 patients receiving a cyclophosphamide-based chemotherapy regimen containing doxorubicin The first 8 mg dose of ondansetron tablets was administered 30 minutes before the start of chemotherapy, with a subsequent dose 8 hours after the first dose, followed by 8 mg of ondansetron tablets twice a day for 2 days after the completion of chemotherapy. The usual dosing for ondansetron for an adult is:

• 8 mg twice a day
• Alternatively, 8 mg three times a day can also be used, but it is not a recommended regimen for the treatment of moderately emetogenic chemotherapy. 2 2

From the Research

Ondansetron Dosing for Adults

• The usual dosing for ondansetron in adults is not explicitly stated in the provided studies, but the studies mention various dosing regimens used in clinical trials 3, 4, 5, 6.
• One study mentions that ondansetron is available in 4- and 8-mg oral tablets 4.
• Another study mentions that ondansetron 4 mg i.v. was administered to patients before induction of general anesthesia, and some patients received a repeat i.v. ondansetron 4 mg dose for postoperative nausea and vomiting (PONV) 6.
• The studies do not provide a clear recommendation for the usual dosing of ondansetron in adults, but they suggest that the dosing regimen may vary depending on the specific clinical context and the patient's response to treatment 3, 4, 5, 6.

Clinical Context

• Ondansetron is used to prevent nausea and vomiting caused by chemotherapy, radiotherapy, and surgery 3, 4, 7, 5, 6.
• The drug is a selective 5-HT3 receptor antagonist, which has been shown to be effective in preventing acute and delayed nausea and vomiting 3, 7, 5.
• Ondansetron is often used in combination with other antiemetic agents, such as dexamethasone, to enhance its efficacy 3, 7, 5.