What is the recommended dosage of Tamiflu (oseltamivir) for a 5-year-old patient weighing 47 pounds with no known contraindications or allergies for the treatment of influenza?

Tamiflu Dosing for a 5-Year-Old Weighing 47 Pounds

For a 5-year-old child weighing 47 pounds (21.3 kg), the recommended oseltamivir dose is 45 mg twice daily for 5 days for treatment of influenza. 1, 2

Weight-Based Dosing Algorithm

This child falls into the >15-23 kg weight category (47 pounds = 21.3 kg), which corresponds to the 45 mg twice daily dosing tier. 3, 1

Specific Dosing Details:

• Treatment dose: 45 mg orally twice daily for 5 days 3, 4
• Volume if using oral suspension: 7.5 mL twice daily (using the 6 mg/mL concentration) 1, 2
• Prophylaxis dose (if applicable): 45 mg once daily for 10 days 3, 1

Critical Timing Considerations

Treatment must be initiated within 48 hours of symptom onset for maximum effectiveness. 2, 4, 5 Starting treatment within 12 hours reduces illness duration by an additional 74.6 hours compared to starting at 48 hours, while starting within 24 hours provides an additional 53.9 hours of benefit. 5

Administration Guidance

Give oseltamivir with food to significantly reduce gastrointestinal side effects. 2, 5, 6 Nausea and vomiting occur in approximately 10-15% of pediatric patients, but these symptoms are mild, transient, and resolve within 1-2 days. 2, 5, 6 Taking the medication with a light snack or meal reduces the likelihood and severity of these effects. 2, 5

Formulation Options

• Capsules: 45 mg capsules can be used if the child can swallow them whole 1, 4
• Oral suspension: If capsules cannot be swallowed, use 7.5 mL of the 6 mg/mL oral suspension twice daily 1, 2, 4
• Capsule contents: If suspension is unavailable, the 45 mg capsule can be opened and mixed with liquid for administration 2

Common Pitfalls to Avoid

Do not confuse this child's weight category with adjacent dosing tiers. 1, 2 The weight-based categories are:

• ≤15 kg (≤33 lb): 30 mg twice daily 3, 1
• >15-23 kg (>33-51 lb): 45 mg twice daily ← This patient 3, 1

• 23-40 kg (>51-88 lb): 60 mg twice daily 3, 1

• 40 kg (>88 lb): 75 mg twice daily 3, 1

Do not use infant dosing formulas (mg/kg dosing) for children ≥1 year of age. 1, 2 The weight-based unit doses (30,45,60,75 mg) are specifically designed for children 1-12 years and should not be replaced with mg/kg calculations. 1, 7, 8

Renal Function Considerations

No dose adjustment is needed for this child unless there is known renal impairment. 3, 2 If creatinine clearance is 10-30 mL/min, reduce the dose to 45 mg once daily (instead of twice daily) for treatment. 3, 2