Recommended Dosing Regimen for Paxlovid (Nirmatrelvir and Ritonavir)
The recommended dosage for Paxlovid 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
Standard Dosing
- Paxlovid should be administered at approximately the same time each morning and evening 1
- The 5-day treatment course should be initiated as soon as possible after COVID-19 diagnosis and within 5 days of symptom onset 1
- Tablets should be swallowed whole and not chewed, broken, or crushed 1
- Paxlovid can be taken with or without food 1
Dosage Adjustments for Renal Impairment
- No dosage adjustment is needed for patients with mild renal impairment (eGFR ≥60 to <90 mL/min) 1
- For patients with 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 1, 2
- For patients with severe renal impairment (eGFR <30 mL/min) including those requiring hemodialysis 1, 2:
- Day 1: 300 mg nirmatrelvir (two tablets) with 100 mg ritonavir (one tablet) once daily
- Days 2-5: 150 mg nirmatrelvir (one tablet) with 100 mg ritonavir (one tablet) once daily
- For hemodialysis patients, administer dose after hemodialysis 1
Dosage Adjustments for Hepatic Impairment
- No dosage adjustment is needed for patients with mild (Child-Pugh Class A) or moderate (Child-Pugh Class B) hepatic impairment 1
- Paxlovid is not recommended for patients with severe hepatic impairment (Child-Pugh Class C) due to lack of pharmacokinetic and safety data 1
Important Drug Interaction Considerations
- Ritonavir is a strong CYP3A inhibitor and perpetrator of many drug-drug interactions 3
- Always check for drug interactions before prescribing Paxlovid using resources like the Liverpool COVID-19 Drug Interaction Tool 3
- High-risk interactions to avoid include 3:
- Antiarrhythmics (amiodarone, flecainide, propafenone)
- Certain anticoagulants (rivaroxaban)
- Some statins (lovastatin, simvastatin)
- The duration of interaction risk extends beyond the 5-day treatment period due to ritonavir's effects on metabolism and clearance 3
Missed Dose Instructions
- If a dose is missed within 8 hours of the scheduled time, take it as soon as possible and resume the normal dosing schedule 1
- If more than 8 hours have passed, skip the missed dose and take the next dose at the regularly scheduled time 1
- Do not double the dose to make up for a missed dose 1
Common Adverse Effects
- Dysgeusia (altered taste) and diarrhea are common adverse effects 3
- Monitor for potential hepatotoxicity 3
Paxlovid has shown significant efficacy in reducing hospitalization and death in high-risk patients with COVID-19 when administered within 5 days of symptom onset 4, 5. Proper dosing according to renal function and careful consideration of drug interactions are essential for safe and effective use.