What is the appropriate oseltamivir (Tamiflu) dosing for a 72‑lb (≈33 kg) patient for treatment of acute influenza and for post‑exposure prophylaxis?

Oseltamivir (Tamiflu) Dosing for a 72‑Pound Patient

For a 72‑pound (≈33 kg) patient, the recommended oseltamivir dose is 60 mg twice daily for 5 days for treatment of influenza, or 60 mg once daily for 10 days for post‑exposure prophylaxis. 1, 2

Weight‑Based Dosing Algorithm

A 72‑pound patient converts to approximately 32.7 kg, which places them in the >23 kg to ≤40 kg (>51 lb to ≤88 lb) weight category. 1, 2

Treatment Regimen (Acute Influenza)

• Dose: 60 mg orally twice daily 1, 2
• Duration: 5 days 1, 2
• Volume (if using oral suspension): 10 mL of the 6 mg/mL suspension per dose 1, 3, 2
• Timing: Initiate within 48 hours of symptom onset for maximum benefit; earlier initiation (within 12–36 hours) yields progressively greater symptom reduction 3, 4

Prophylaxis Regimen (Post‑Exposure)

• Dose: 60 mg orally once daily 1, 2
• Duration: 10 days after close contact with an infected individual 1, 2
• Community outbreak: May extend up to 6 weeks during widespread influenza activity 3, 2
• Timing: Begin within 48 hours of exposure 3, 2

Formulation Options

Oral Suspension (Preferred for Accurate Dosing)

• Concentration: 6 mg/mL after reconstitution 1, 2
• Volume for 60 mg dose: 10 mL 1, 3, 2
• Measurement: Use a calibrated oral dosing device; household spoons are inadequate 3, 2

Capsules

• Available strengths: 30 mg, 45 mg, 75 mg 1, 2
• For 60 mg dose: Administer two 30‑mg capsules 1
• Alternative: Capsules may be opened and mixed with sweetened liquid if swallowing is difficult 1

Administration Guidance

• With or without food: May be taken either way, but administration with meals significantly reduces nausea and vomiting (the most common adverse effects, occurring in 10–15% of patients) 1, 3, 5
• Do not discontinue early: Complete the full 5‑day treatment course even if symptoms improve before day 5; early cessation may promote viral resistance 3

Critical Dosing Pitfalls to Avoid

• Do not round up to 75 mg: A 72‑pound (33 kg) patient remains in the >23–40 kg bracket and should receive 60 mg, not the 75 mg dose reserved for patients >40 kg (>88 lb) 1, 3, 2
• Do not use age‑based dosing: Weight‑based dosing takes precedence over age for children ≥12 months 1, 3, 6
• Do not delay treatment: Efficacy declines sharply after 48 hours from symptom onset; every 12‑hour delay reduces benefit by approximately 25% 3, 4
• Do not confuse treatment and prophylaxis regimens: Treatment is twice daily for 5 days; prophylaxis is once daily for 10 days 1, 2

Renal Function Considerations

• Normal renal function: No dose adjustment required 1, 3
• Creatinine clearance 10–30 mL/min: Reduce treatment dose to 30 mg once daily (instead of 60 mg twice daily) for 5 days; prophylaxis dose becomes 30 mg once daily or 75 mg every other day for 10 days 1, 3, 2
• Creatinine clearance <10 mL/min: Oseltamivir is not recommended for patients with end‑stage renal disease not on dialysis 3

Expected Clinical Benefits

• Symptom duration reduction: Treatment shortens illness by approximately 1–1.5 days (24–36 hours) compared with placebo when initiated within 48 hours 3, 7
• Complication reduction: Modest reduction in investigator‑mediated unverified pneumonia (number needed to treat = 100) 7
• Prophylaxis efficacy: Reduces symptomatic influenza by 55% in individual prophylaxis and 13.6% in household prophylaxis 7

Common Adverse Effects

• Gastrointestinal: Nausea (3.7% increased risk), vomiting (4.6% increased risk in adults, 5.3% in children) 3, 7
• Neuropsychiatric: Headache (3.2% increased risk in prophylaxis), psychiatric events (1.1% increased risk in prophylaxis) 7
• Renal: Rare renal events (0.67% increased risk in prophylaxis) 7
• Discontinuation rate: Only 1.8% of patients discontinue due to adverse effects 4

Special Populations

• Immunocompromised patients: May extend prophylaxis up to 12 weeks during community outbreaks 3, 2
• High‑risk patients: Treatment is recommended regardless of time from symptom onset for patients with chronic conditions (asthma, diabetes, immunosuppression, cardiac disease) 1
• Pregnancy: Oseltamivir may be used when benefits outweigh risks; no absolute contraindication exists 3