Oseltamivir Dosing for a 79-Year-Old Adult
For a 79-year-old adult with normal renal function (creatinine clearance ≥30 mL/min), the recommended dose is oseltamivir 75 mg orally twice daily for 5 days for treatment, or 75 mg once daily for 10 days for prophylaxis. 1, 2
Standard Adult Dosing
- The standard adult dose of oseltamivir is 75 mg twice daily for 5 days when treating influenza infection 1
- For prophylaxis, the dose is 75 mg once daily for 10 days after exposure 1
- Age alone does not require dose reduction—the critical factor is renal function, not chronological age 1, 2
Critical Renal Function Assessment
You must assess creatinine clearance before dosing, as the threshold for dose adjustment is CrCl <30 mL/min, not age-based. 2, 3
Dosing Based on Renal Function:
Normal to Mild Impairment (CrCl ≥30 mL/min):
- Treatment: 75 mg twice daily for 5 days 1, 2, 4
- Prophylaxis: 75 mg once daily for 10 days 1, 2, 4
- No dose adjustment needed 2, 3
Moderate Impairment (CrCl 10-30 mL/min):
- Treatment: 75 mg once daily (not twice daily) for 5 days 1, 2
- Prophylaxis: 30 mg once daily OR 75 mg every other day for 10 days (5 total doses) 1, 2
Severe Impairment (CrCl <10 mL/min or hemodialysis):
- Treatment: 30 mg per hemodialysis cycle 2, 4
- Prophylaxis: 30 mg every alternate hemodialysis cycle 2, 4
Administration Considerations
- Take with food to reduce gastrointestinal side effects (nausea/vomiting occur in approximately 1 in 7 patients) 1, 2, 3, 5
- Available as 30 mg, 45 mg, and 75 mg capsules, or oral suspension (6 mg/mL when reconstituted) 1, 3
- Timing matters: initiate within 48 hours of symptom onset for maximum benefit 5, 6
Common Pitfalls to Avoid
- Do not confuse GFR with creatinine clearance—the 30 mL/min threshold applies to creatinine clearance specifically 2
- Do not assume elderly patients automatically need dose reduction—only reduce dose if CrCl <30 mL/min 1, 2
- Do not delay treatment while awaiting laboratory confirmation—empiric treatment should begin promptly if influenza is suspected clinically 1
- In elderly patients, renal function often declines with age, so calculating CrCl (not just looking at serum creatinine) is essential 1, 4
Special Consideration for Elderly Patients
While the 2002 ACIP guidelines suggested a 100 mg/day dose for patients >65 years when using amantadine or rimantadine due to age-related renal decline 1, current guidelines for oseltamivir do not recommend age-based dose reduction 1, 2. The decision is based solely on measured creatinine clearance, as pharmacokinetic studies show oseltamivir carboxylate exposure is inversely proportional to renal function, not age 4, 7.