What is the standard dose of Paxlovid (nirmatrelvir/ritonavir) for treating COVID-19?

Standard Dosage of Paxlovid for COVID-19 Treatment

The standard 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

Dosing Information

Paxlovid is a co-packaged medication containing nirmatrelvir tablets and ritonavir tablets. The components must be taken together to be effective. The standard dosing regimen includes:

• Initial dose: 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet)
• Frequency: Twice daily
• Duration: 5 days
• Administration: Take orally with or without food 1
• Timing: Administer at approximately the same time each day 1

Dosage Adjustments for Special Populations

Renal Impairment

• Moderate renal impairment (eGFR ≥30 to <60 mL/min):

  • 150 mg nirmatrelvir (one 150 mg tablet) with 100 mg ritonavir (one 100 mg tablet) twice daily for 5 days 2, 1

• Severe renal impairment (eGFR <30 mL/min) including those requiring hemodialysis:

  • Day 1: 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet) once
  • Days 2-5: 150 mg nirmatrelvir (one 150 mg tablet) with 100 mg ritonavir (one 100 mg tablet) once daily 2, 1
  • For patients on hemodialysis, the dose should be administered after hemodialysis 1

Hepatic Impairment

• Paxlovid is not recommended in patients with severe hepatic impairment (Child-Pugh Class C) 1

Important Clinical Considerations

Timing of Treatment

• Initiate Paxlovid treatment as soon as possible after diagnosis of COVID-19 and within 5 days of symptom onset 2, 1

Drug Interactions

• Ritonavir is a strong CYP3A inhibitor that can cause significant drug-drug interactions 2
• Prior to prescribing Paxlovid, review all medications taken by the patient to assess potential drug-drug interactions 1
• Avoid co-administration with drugs highly dependent on CYP3A for clearance where elevated concentrations could lead to serious reactions 2, 1

Clinical Efficacy

Paxlovid has demonstrated significant efficacy in reducing hospitalization and death in high-risk patients with COVID-19 when initiated early in the disease course 3. A recent study using electronic health record data showed that Paxlovid reduced the risk of hospitalization by 39% and the risk of death by 61% 3.

Common Pitfalls and Caveats

1. Drug interactions: Ritonavir, a component of Paxlovid, is a strong CYP3A inhibitor that can interact with many medications. Always check for potential interactions before prescribing.

2. Timing of initiation: Effectiveness is maximized when treatment is started within 5 days of symptom onset. Delayed initiation may reduce efficacy.

3. Renal function assessment: Always assess renal function before prescribing, as dose adjustments are required for patients with renal impairment.

4. Adherence: Emphasize the importance of completing the full 5-day course of treatment for optimal efficacy.

5. Contraindications: Paxlovid is contraindicated in patients with a history of clinically significant hypersensitivity reactions to nirmatrelvir or ritonavir 1.

The standard dosing of Paxlovid represents a balance between achieving therapeutic concentrations of nirmatrelvir (maintained above the EC90 for SARS-CoV-2) while managing the pharmacokinetic profile through ritonavir co-administration 4.