What is the dosing regimen for Zofran (ondansetron) for nausea and vomiting?

Ondansetron (Zofran) Dosing Regimen for Nausea and Vomiting

The standard dosing regimen for ondansetron (Zofran) is 8 mg IV administered over 15 minutes for acute nausea and vomiting, or 8 mg orally twice daily for prevention and management of nausea and vomiting. 1

Intravenous Dosing

• For chemotherapy-induced nausea and vomiting (CINV), administer 8 mg IV 30 minutes before chemotherapy, with potential additional doses 8 hours after the first dose 1
• IV administration should be given over 15 minutes to minimize side effects 1

Oral Dosing

• For prevention of CINV: 8 mg orally twice daily is the recommended dosage 2, 3
• For delayed nausea/vomiting (1-2 days after chemotherapy): continue with 8 mg orally every 12 hours for up to 2-3 days after chemotherapy 1
• For medication-induced nausea: "as needed" (prn) approach is appropriate rather than scheduled dosing 2

Dosing Based on Clinical Scenario

Highly Emetogenic Chemotherapy

• A single 24 mg oral dose administered 30 minutes prior to chemotherapy is superior to other regimens 3
• 56% of patients receiving a single 24 mg oral dose experienced no nausea during the 24-hour trial period 3
• Note: 8 mg twice daily and 32 mg once daily regimens are not recommended for highly emetogenic chemotherapy 3

Moderately Emetogenic Chemotherapy

• 8 mg orally administered 30 minutes before chemotherapy, with a subsequent dose 8 hours after the first dose, followed by 8 mg twice daily for 2 days after completion of chemotherapy 3, 4
• This regimen was significantly more effective than placebo, with 61% of patients having no emetic episodes during a 3-day study period 4
• The twice-daily regimen may encourage better patient compliance compared to three-times-daily dosing 4

Important Considerations

• QT interval prolongation is a concern with high-dose ondansetron (32 mg IV), but this is less of a concern with standard doses 1
• For refractory cases, consider adding agents from different classes (such as dopamine antagonists like metoclopramide) or switching to a different 5-HT3 antagonist 1, 2
• Common side effects include headache, constipation, diarrhea, and transient abnormalities in liver function tests 5
• The elimination half-life is approximately 3.5 hours in healthy volunteers but may be extended in elderly patients (mean of 7.9 hours) 5

Alternative Options for Breakthrough Nausea

• Prochlorperazine 5-10 mg orally every 6 hours as needed 2
• Metoclopramide 5-20 mg orally every 6-8 hours as needed 2
• Dexamethasone 4 mg orally for refractory cases 2

Monitoring

• Assess effectiveness of antiemetic therapy after initiation 2
• If nausea persists despite as-needed ondansetron, consider switching to scheduled dosing or adding another antiemetic agent 2