Paxlovid Dosing Verification
Yes, this is correct. The standard Paxlovid dose pack contains 300 mg nirmatrelvir (two 150 mg tablets) plus 100 mg ritonavir (one 100 mg tablet), taken together twice daily for 5 days 1, 2.
Standard Dosing Regimen
The FDA-approved dosing for patients with normal to mild renal impairment (eGFR ≥60 mL/min) is:
- Nirmatrelvir 300 mg (two 150 mg tablets)
- Plus ritonavir 100 mg (one 100 mg tablet)
- All 3 tablets taken together orally twice daily (morning and bedtime)
- Duration: 5 days 2, 3
This regimen achieves therapeutic nirmatrelvir concentrations of approximately 3.43 µg/mL at peak and 1.57 µg/mL at trough on day 5, which are 11.7× and 5.4× above the antiviral EC90, respectively 4.
Dose Pack Configurations
Three different dose packs exist 2:
- Standard pack (300 mg/100 mg): For normal/mild renal impairment - 10 blister cards, each containing 2 nirmatrelvir 150 mg tablets + 1 ritonavir 100 mg tablet
- Moderate renal impairment pack (150 mg/100 mg): For eGFR 30-59 mL/min - reduced to 1 nirmatrelvir tablet + 1 ritonavir tablet twice daily
- Severe renal impairment pack: For eGFR <30 mL/min - 300 mg/100 mg on Day 1, then 150 mg/100 mg once daily on Days 2-5 2, 5
Critical Prescribing Points
Nirmatrelvir must be co-administered with ritonavir. Failure to do so results in insufficient nirmatrelvir plasma levels due to rapid CYP3A4 metabolism 2, 4. Ritonavir acts as a pharmacokinetic enhancer by inhibiting CYP3A4, shifting nirmatrelvir elimination from hepatic to primarily renal 4.
Initiate within 5 days of symptom onset for maximum benefit - this timing achieved an 89% relative risk reduction in hospitalization or death in the pivotal trial 6.
Drug interactions are extensive due to ritonavir's potent CYP3A4 inhibition. In one French cohort, 86.7% of patients had at least one clinically relevant interaction, with statins (17.7%), immunosuppressants (12.0%), and direct oral anticoagulants (10.5%) being most common 7. Use the Liverpool COVID-19 drug interaction tool before prescribing 1.