Paxlovid Dosage for Normal Renal Function
The recommended dosage of Paxlovid for adults with normal renal function is 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet), taken together orally twice daily for 5 days. 1
Dosing Details
The standard treatment course for Paxlovid consists of:
- Nirmatrelvir: 300 mg (two 150 mg tablets)
- Ritonavir: 100 mg (one 100 mg tablet)
- Frequency: Twice daily (morning and evening)
- Duration: 5 days
- Administration: Tablets should be swallowed whole and not chewed, broken, or crushed
- Timing: Can be taken with or without food 1
Renal Function Considerations
Renal function significantly impacts Paxlovid dosing:
Normal renal function or mild impairment (eGFR ≥60 mL/min): Standard dose of 300 mg nirmatrelvir with 100 mg ritonavir twice daily 2, 1
Moderate renal impairment (eGFR ≥30 to <60 mL/min): Reduced dose of 150 mg nirmatrelvir with 100 mg ritonavir twice daily 1
Severe renal impairment (eGFR <30 mL/min): Special dosing regimen of 300 mg nirmatrelvir with 100 mg ritonavir on Day 1, followed by 150 mg nirmatrelvir with 100 mg ritonavir on Days 2-5 2, 1
Pharmacokinetic Rationale
The dose adjustment in renal impairment is necessary because:
- Nirmatrelvir is primarily eliminated by the kidneys when co-administered with ritonavir 3
- Systemic exposure increases significantly with declining renal function:
Important Clinical Considerations
- Paxlovid should be initiated as soon as possible after COVID-19 diagnosis and within 5 days of symptom onset 1
- The full 5-day treatment course should be completed to maximize viral clearance 1
- If a dose is missed within 8 hours of the scheduled time, it should be taken as soon as possible; if more than 8 hours have passed, skip the missed dose and take the next dose at the regular time 1
- Significant drug interactions are possible due to ritonavir's strong CYP3A4 inhibition - a thorough medication review is essential before prescribing 1, 4
Common Pitfalls to Avoid
- Failure to co-administer both components: Nirmatrelvir must always be given with ritonavir to maintain therapeutic levels 1
- Incorrect dosing in renal impairment: Using standard dosing in patients with moderate or severe renal impairment can lead to toxicity 3
- Overlooking drug interactions: Ritonavir is a strong CYP3A inhibitor that can significantly affect the metabolism of many medications 1, 4
- Premature discontinuation: Not completing the full 5-day course may reduce effectiveness 1
Remember that Paxlovid has shown significant efficacy in reducing the risk of COVID-19-related hospitalization and death when properly dosed according to renal function 2.