What is the appropriate dose of ondansetron (Zofran) for a patient weighing 50.10 kg?

Ondansetron Dosing for a 50.10 kg Patient

For a patient weighing 50.10 kg, the appropriate dose of ondansetron is 8 mg orally or intravenously, with a maximum daily dose of 16 mg. 1

Dosing Guidelines Based on Clinical Setting

Oral Administration

• Standard oral dose: 8 mg tablet
• Frequency: Every 8-12 hours as needed
• Maximum daily dose: 16 mg

Intravenous Administration

• Standard IV dose: 8 mg or 0.15 mg/kg (7.5 mg for this patient)
• Administration rate: Over 15 minutes
• Maximum single dose: 8 mg
• Maximum daily dose: 16 mg

Weight-Based Considerations

For this 50.10 kg patient, there are two approaches:

1. Fixed dosing: 8 mg (standard adult dose)
2. Weight-based dosing: 0.15 mg/kg = 7.5 mg

Since the patient weighs just over 50 kg, the standard adult dosing of 8 mg is appropriate. The FDA-approved dosing indicates that for patients weighing 50 kg, the standard adult dose applies 1.

Clinical Setting-Specific Dosing

For Chemotherapy-Induced Nausea and Vomiting

• Moderate emetic risk: 8 mg IV or PO before chemotherapy 2
• High emetic risk: 8 mg IV or PO before chemotherapy, may repeat every 8 hours 2

For Radiation-Induced Nausea and Vomiting

• Single dose: 8 mg PO 1-2 hours before radiotherapy 1
• Maintenance: 8 mg PO every 8 hours as needed 1

For Postoperative Nausea and Vomiting

• Prophylaxis: 8 mg IV or PO before anesthesia induction 1
• Treatment: 4 mg IV for breakthrough nausea/vomiting 1

For Pediatric Patients with Gastroenteritis (for reference)

• For children over 4 years: 0.15 mg/kg 3
• Maximum dose: 8 mg for children 4-11 years, 16 mg for children 12+ years 3

Important Considerations

• QT prolongation risk: Monitor for cardiac effects, especially with higher doses or IV administration 4
• Hepatic impairment: No dose adjustment needed for this patient unless severe hepatic dysfunction is present 1
• Renal impairment: No dose adjustment needed as renal clearance represents only 5% of overall clearance 1
• Administration timing: For maximum efficacy, administer at least 30 minutes before the anticipated nausea-inducing event 5
• Half-life: Approximately 3.8 hours in adults, so dosing every 8 hours is appropriate for continuous control 5

Conclusion

For this 50.10 kg patient, the standard adult dose of 8 mg ondansetron (oral or IV) is appropriate, not exceeding 16 mg in 24 hours. The specific administration schedule should be determined by the clinical indication (chemotherapy, radiation, post-operative, etc.).