Maximum Recommended Dose of Ondansetron (Zofran)
The maximum recommended dose of ondansetron (Zofran) is 24 mg orally or 16 mg intravenously in a 24-hour period for adults. 1, 2
Dosing by Administration Route
Oral Administration
- Standard oral dose is 8 mg per administration 3
- For highly emetogenic chemotherapy, a single 24 mg oral dose is recommended and has shown superior efficacy compared to other dosing regimens 1, 4
- Oral formulations include tablets, oral dissolving tablets, and oral soluble film, all bioequivalent at the same dose 5
Intravenous Administration
- For breakthrough nausea/vomiting, ondansetron can be titrated up as needed to a maximum of 16 mg IV daily 2
- For chemotherapy-induced nausea and vomiting, the standard IV dose is 8-16 mg 6
Dosing by Clinical Scenario
Highly Emetogenic Chemotherapy
- For high emetic risk chemotherapy, ondansetron is typically given on day 1 only at a dose of 16-24 mg PO or 8-16 mg IV 6
- A single 24 mg oral dose has demonstrated better efficacy than 8 mg twice daily or 32 mg once daily regimens 1, 4
Moderately Emetogenic Chemotherapy
- For moderate emetic risk chemotherapy, ondansetron can be given on days 1-3 2
- Dosing options include 16-24 mg PO once or 8-16 mg IV once 6
Low Emetogenic Chemotherapy
- For low emetic risk chemotherapy, a single dose of ondansetron before chemotherapy is recommended, with additional doses only as needed for breakthrough symptoms 2
Radiation Therapy
- For radiation therapy-induced nausea and vomiting, ondansetron 8 mg can be administered once to twice daily on days of radiation therapy 6, 3
- For high-risk radiation therapy: 8 mg oral or IV once daily to twice daily 6
Special Population Considerations
Hepatic Impairment
- In patients with severe hepatic impairment (Child-Pugh score ≥10), clearance is reduced 2-3 fold with increased half-life to 20 hours, requiring dose adjustment 1
- For these patients, the total daily dose should not exceed 8 mg 1
Elderly Patients
- Elderly patients have slightly reduced clearance of ondansetron, but no specific dose adjustment is required unless other factors are present 1, 7
Pediatric Patients
- Pediatric dosing is typically 0.15 mg/kg IV for three doses on the day of chemotherapy 7, 8
- Maximum pediatric dose should not exceed adult maximum recommendations 8
Important Clinical Considerations
- Monitoring for QT interval prolongation is advised when using ondansetron at higher doses, particularly in patients with cardiac risk factors 3
- Ondansetron undergoes extensive hepatic metabolism, with only about 5% eliminated unchanged in urine 1, 7
- The half-life of ondansetron is approximately 3.5-4 hours in healthy adults 1, 7
While alternative routes of administration such as nasal delivery have been studied 9, they are not currently approved for clinical use and do not change the maximum recommended daily dose.