What is the recommended dosage of Zofran (ondansetron) for preventing chemotherapy-induced nausea and vomiting?

Recommended Dosage of Ondansetron (Zofran) for Chemotherapy-Induced Nausea and Vomiting

For highly emetogenic chemotherapy, a single 24 mg oral dose of ondansetron administered 30 minutes before chemotherapy is the recommended dosage. 1

Dosage Recommendations Based on Emetogenic Potential

Highly Emetogenic Chemotherapy

• Single 24 mg oral dose administered 30 minutes before chemotherapy 1
• Intravenous alternative: 8 mg IV administered 30 minutes before chemotherapy 2
• Note: 8 mg twice daily and 32 mg once daily regimens are not recommended for highly emetogenic chemotherapy 1

Moderately Emetogenic Chemotherapy

• First dose: 8 mg oral or IV administered 30 minutes before chemotherapy 1
• Second dose: 8 mg oral administered 8 hours after the first dose 1
• Maintenance: 8 mg oral twice daily for 1-2 days after completion of chemotherapy 1, 3

Administration Guidelines

• Antiemetics should be given prophylactically 30-60 minutes before the start of chemotherapy 2
• For oral administration, ondansetron is typically given once daily 2
• If the patient experiences breakthrough nausea and vomiting during treatment, ondansetron should be administered intravenously 2

Combination Therapy Recommendations

• For optimal control of chemotherapy-induced nausea and vomiting, ondansetron is often combined with:
  • Corticosteroids (typically dexamethasone 20 mg IV for cisplatin-based regimens or 8 mg IV for cyclophosphamide/anthracycline-based regimens) 2
  • NK1 receptor antagonists (e.g., aprepitant) for highly emetogenic regimens 2

Special Considerations

• For multiple-day chemotherapy: Use the acute nausea and vomiting protocol on chemotherapy days, followed by delayed nausea and vomiting protocol for 1-2 days after chemotherapy 2
• For refractory nausea and vomiting: Consider adding dopamine antagonists to the ondansetron and corticosteroid regimen 2
• For high-dose chemotherapy: Use full doses of ondansetron intravenously along with corticosteroids 2

Common Pitfalls and Caveats

• Ondansetron is primarily effective for acute nausea and vomiting (within first 24 hours); its efficacy for delayed symptoms is improved when combined with dexamethasone 3
• Maintenance therapy with oral ondansetron after 24 hours is more effective than placebo in preventing delayed nausea and emesis 3
• The efficacy of ondansetron is generally maintained over multiple courses of chemotherapy 3
• Common side effects include headache, constipation, and occasionally diarrhea 4
• In patients with severe hepatic impairment, dose adjustment may be necessary due to reduced clearance and increased half-life 1