What is the recommended dose for Paxlovid (nirmatrelvir/ritonavir)?

Recommended Dosage for Paxlovid (Nirmatrelvir/Ritonavir)

The standard 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

Dosing Details

Standard Dosing

• For patients with normal renal function or mild renal impairment (eGFR ≥60 mL/min):
  • 300 mg nirmatrelvir (two 150 mg tablets) + 100 mg ritonavir (one 100 mg tablet)
  • Taken twice daily (morning and evening) for 5 days
  • Can be taken with or without food

Dosing Adjustments for Renal Impairment

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

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

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

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

Hepatic Impairment Considerations

• No dosage adjustment needed for mild (Child-Pugh Class A) or moderate (Child-Pugh Class B) hepatic impairment
• Not recommended for use in patients with severe hepatic impairment (Child-Pugh Class C) 1

Administration Guidelines

• Treatment should be initiated as soon as possible after COVID-19 diagnosis and within 5 days of symptom onset
• All tablets should be swallowed whole (not chewed, broken, or crushed)
• Complete the full 5-day treatment course to maximize viral clearance
• If a dose is missed within 8 hours of the scheduled time, take it as soon as possible and resume normal schedule
• If more than 8 hours have passed, skip the missed dose and take the next dose at the regular time (do not double the dose) 1

Important Considerations

Drug Interactions

• Ritonavir is a strong CYP3A4 inhibitor that can cause significant drug-drug interactions
• Before prescribing, assess for potential drug-drug interactions using resources like the Liverpool COVID-19 Drug Interaction Tool
• Certain medications are contraindicated with Paxlovid, including:
  • Alfuzosin, amiodarone, certain statins (lovastatin, simvastatin), midazolam, triazolam
  • Strong CYP3A inducers (carbamazepine, phenytoin, rifampin, St. John's wort)
  • Other medications that may cause serious adverse events when levels are increased 1, 2

Efficacy

Clinical trials demonstrated that Paxlovid reduced the risk of COVID-19-related hospitalization or death by approximately 89% when administered within 3 days of symptom onset 3. Real-world data shows a 39% reduction in hospitalization risk and 61% reduction in death risk 4.

Common Side Effects

• Dysgeusia (altered taste) - occurs in approximately 5.6% of patients
• Diarrhea - occurs in approximately 3.1% of patients
• Other potential side effects include nausea and fatigue 3, 5

Special Populations

Elderly

• No specific dose adjustment required based on age alone
• Older patients (65+ years) show greater absolute risk reduction for hospitalization with Paxlovid treatment 4

Pregnancy

• Paxlovid represents an option for pregnant people with COVID-19 to reduce disease progression risk
• The WHO acknowledges uncertainty regarding potential adverse reactions in pregnant or breastfeeding individuals, though no serious reactions have been reported 5

Remember that Paxlovid must be prescribed with careful consideration of the patient's complete medication list due to the significant potential for drug interactions caused by ritonavir.