Recommended Dosage of Paxlovid for COVID-19 Treatment
The standard recommended dose of Paxlovid is 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet), with all three tablets taken together twice daily for 5 days. 1, 2
Standard Dosing Regimen
- Initiate treatment as soon as possible after diagnosis and within 5 days of symptom onset
- Administer orally with or without food
- Take at approximately the same time each day
- Complete the full 5-day treatment course
Dose Adjustments for Special Populations
Renal Impairment 1, 2
Moderate renal impairment (eGFR ≥30 to <60 mL/min):
- 150 mg nirmatrelvir (one tablet) with 100 mg ritonavir (one tablet) twice daily for 5 days
Severe renal impairment (eGFR <30 mL/min) including those requiring hemodialysis:
- Day 1: 300 mg nirmatrelvir (two tablets) with 100 mg ritonavir (one tablet) once
- Days 2-5: 150 mg nirmatrelvir (one tablet) with 100 mg ritonavir (one tablet) once daily
- For hemodialysis patients, administer after hemodialysis
Hepatic Impairment 1, 2
- No dose adjustment needed for mild to moderate hepatic impairment
- Not recommended for patients with severe hepatic impairment (Child-Pugh Class C)
Important Clinical Considerations
Drug Interactions
- Ritonavir is a strong CYP3A inhibitor that can significantly affect the metabolism of many medications 1
- Prior to prescribing:
- Review all medications to assess potential drug-drug interactions
- Determine if concomitant medications require dose adjustment, interruption, or additional monitoring
- Consider using the Liverpool COVID-19 drug interaction tool 2
Contraindications 1
- History of clinically significant hypersensitivity reactions to nirmatrelvir or ritonavir
- Co-administration with drugs highly dependent on CYP3A for clearance where elevated concentrations may cause serious reactions
- Co-administration with potent CYP3A inducers that may reduce nirmatrelvir/ritonavir plasma concentrations
Efficacy
- Paxlovid has demonstrated significant efficacy in reducing the risk of COVID-19 progression to severe disease, with a reported 89% reduction in risk of hospitalization or death when initiated within 3 days of symptom onset 2
- Real-world data suggests that Paxlovid treatment can shorten disease course by reducing viral load even when initiated beyond the 5-day window 3
Common Adverse Effects
- Most common adverse reactions (≥1% incidence) are dysgeusia (altered taste) and diarrhea 1
- Most adverse events are mild in severity 2
Monitoring Recommendations
- Assess kidney and hepatic function at baseline and during treatment 1
- Discontinue use if ALT levels increase to ≥5 times the upper limit of normal or if any ALT elevation is accompanied by signs of liver inflammation 1
Paxlovid's dosing regimen has been established based on pharmacokinetic studies showing that the standard dose maintains nirmatrelvir plasma concentrations well above the antiviral EC90 value needed for effective SARS-CoV-2 inhibition 4, while dose adjustments for renal impairment ensure appropriate drug exposure across different patient populations 5.