Paxlovid Dosing: Standard Regimen
A patient takes 3 tablets twice daily: two 150 mg nirmatrelvir tablets (total 300 mg) plus one 100 mg ritonavir tablet, taken together at approximately the same time each day for 5 days. 1
Standard Dosing for Normal Renal Function
- Total daily intake: 6 tablets per day (3 tablets twice daily) 1
- Per dose composition:
- Nirmatrelvir: 300 mg (two 150 mg tablets)
- Ritonavir: 100 mg (one 100 mg tablet) 1
- Duration: 5 days of treatment 1
- Timing: Administer at approximately the same time each day, with or without food 1
- Treatment initiation: Must start within 5 days of symptom onset 2, 1
Dose Adjustments for Renal Impairment
Moderate renal impairment (eGFR 30-59 mL/min):
- Reduced dose: 1 tablet of nirmatrelvir 150 mg plus 1 tablet of ritonavir 100 mg twice daily for all 5 days 2, 1
- Total tablets per dose: 2 tablets (instead of 3) 1
Severe renal impairment (eGFR <30 mL/min) including hemodialysis:
- Day 1: 2 tablets nirmatrelvir 150 mg (300 mg total) plus 1 tablet ritonavir 100 mg once daily 1
- Days 2-5: 1 tablet nirmatrelvir 150 mg plus 1 tablet ritonavir 100 mg once daily 1
- Hemodialysis timing: Administer after hemodialysis on dialysis days 1
Critical Safety Considerations
Drug interactions are the primary concern because ritonavir is a potent CYP3A inhibitor that can cause severe, life-threatening interactions with many medications 1:
- Always check the Liverpool COVID-19 Drug Interaction Tool before prescribing 2, 3
- Contraindicated with drugs highly dependent on CYP3A clearance 1
- Interaction risk extends beyond the 5-day treatment period 3
Common pitfall: Failing to adjust dose for renal impairment—always assess eGFR before prescribing, as nirmatrelvir is primarily renally eliminated when co-administered with ritonavir 4, 5