What is the maximum daily dose of ondansetron (Zofran)?

Maximum Daily Dose of Ondansetron (Zofran)

The maximum daily oral dose of ondansetron is 24 mg, typically administered as a once-daily dose or divided into multiple doses. 1, 2

Dosing Guidelines by Route of Administration

Oral Administration

• Standard oral dose range: 16-24 mg daily 1
• Common dosing schedules:
  • 8 mg twice daily (total 16 mg/day) 3
  • 8 mg three times daily (total 24 mg/day) 3
  • Single 16 mg dose for postoperative nausea/vomiting 3

Intravenous Administration

• Standard IV dose: 8 mg 1
• Maximum single IV dose: 8 mg (FDA revised previous 32 mg IV dosing due to cardiac safety concerns) 4

Dosing Considerations by Clinical Scenario

Chemotherapy-Induced Nausea and Vomiting

• Moderately emetogenic chemotherapy:
  • 8 mg PO 30 minutes before chemotherapy, followed by 8 mg PO 8 hours later, then 8 mg PO twice daily for 1-2 days 2, 3
  • Alternative: 8 mg PO three times daily (not recommended over twice daily regimen) 3

Radiation-Induced Nausea and Vomiting

• Total body irradiation: 8 mg PO 1.5 hours before each radiation fraction 3
• Daily fractionated radiotherapy: 8 mg PO 1-2 hours before radiation, then approximately every 8 hours 3

Postoperative Nausea and Vomiting

• Single dose: 16 mg PO one hour before anesthesia induction 3

Special Populations

Hepatic Impairment

• Severe hepatic dysfunction (Child-Pugh score ≥10): Maximum daily dose should be limited to 8 mg 2

Pediatric Patients

• Pediatric dosing ranges from 4 mg to 24 mg daily for 3 days, with dosing based on age and weight 3
• Children <12 years: 4 mg three times daily
• Children 12-18 years: 8 mg three times daily

Clinical Pearls and Caveats

• Ondansetron should be administered at least 30 minutes before chemotherapy for optimal effect 5
• The twice-daily regimen (8 mg twice daily) has been shown to be as effective as the three-times-daily regimen (8 mg three times daily) for moderately emetogenic chemotherapy, which may improve patient compliance 6
• When combined with aprepitant, no dose adjustment of ondansetron is required 2
• Common side effects include headache and constipation 7, 8
• Cardiac safety concerns exist with high IV doses (32 mg), but standard oral dosing up to 24 mg daily appears to have a favorable safety profile 4

Administration Timing

• For chemotherapy: First dose 30 minutes before chemotherapy 2
• For radiation therapy: 1-2 hours before radiation 3
• For surgery: One hour before anesthesia induction 3

Remember that ondansetron is completely and rapidly absorbed from the gastrointestinal tract, with peak plasma concentrations occurring 0.5-2 hours after oral administration 5, making proper timing of administration critical for optimal antiemetic effect.