Paxlovid Dosing in a 94-Year-Old with Normal GFR
For a 94-year-old patient with normal GFR, the standard Paxlovid dose of 300 mg nirmatrelvir with 100 mg ritonavir twice daily for 5 days is recommended, but close monitoring for drug accumulation is warranted given advanced age. 1
Standard Dosing for Normal Renal Function
The FDA-approved dose is nirmatrelvir 300 mg (two 150 mg tablets) with ritonavir 100 mg (one 100 mg tablet) taken together orally twice daily for 5 days in patients with normal renal function (eGFR ≥60 mL/min). 1
No dose adjustment is required for mild renal impairment (eGFR ≥60 to <90 mL/min), which may be relevant even in elderly patients with "normal" GFR by laboratory values. 1
Treatment should be initiated within 5 days of symptom onset for optimal efficacy. 2
Critical Age-Related Considerations
Advanced age significantly increases the risk of excessive plasma drug concentrations, even with normal renal function. The evidence shows:
Patients older than 65 years have an 11-fold higher risk (OR 11.2,95% CI 1.04-120.4) of achieving excessive plasma trough concentrations above therapeutic targets compared to younger patients. 3
In real-world therapeutic drug monitoring, the geometric mean nirmatrelvir trough concentration was 4997 ng/mL, which is more than double the reference value of 2210 ng/mL stated in product characteristics. 3
Advanced age was identified as a key factor associated with higher plasma concentrations, independent of renal function. 3
Practical Monitoring Recommendations
Given the patient's advanced age of 94 years, implement the following safeguards:
Screen rigorously for drug-drug interactions before prescribing, as ritonavir is a potent CYP3A4 inhibitor that can cause significant interactions with many medications commonly used in elderly patients. 2, 1
Monitor for adverse events closely, particularly during the first 3 days of treatment when drug accumulation is most likely. 3
If the patient is on any renally eliminated comedications, consider even closer monitoring as this combination (advanced age + renally excreted drugs) was associated with the highest plasma concentrations observed. 3
Verify renal function is truly normal and stable, as elderly patients may have age-related decline in renal function not fully captured by eGFR calculations. 2
Administration Details
All three tablets (two nirmatrelvir 150 mg + one ritonavir 100 mg) should be taken together twice daily, approximately 12 hours apart. 1
Tablets can be taken with or without food and should be swallowed whole, not chewed, broken, or crushed. 1
Complete the full 5-day course even if symptoms improve to maximize viral clearance. 1
Common Pitfall to Avoid
Do not automatically reduce the dose based solely on age. The FDA dosing is based on renal function, not age. 1 However, the heightened risk of drug accumulation in this 94-year-old patient means that while you start with standard dosing, you must maintain vigilant monitoring for adverse effects that might signal excessive drug levels. 3