Paxlovid (Nirmatrelvir/Ritonavir) Dosing for a 12-Year-Old
For a 12-year-old patient, the recommended dosing of Paxlovid (nirmatrelvir/ritonavir) is 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet) taken together orally twice daily for 5 days, provided the child weighs at least 40 kg (88 lb). 1
Weight-Based Dosing Considerations
The dosing of Paxlovid for pediatric patients is weight-dependent:
- For patients weighing >40 kg (>88 lb): Standard adult dose of 300 mg nirmatrelvir with 100 mg ritonavir twice daily for 5 days
- For patients weighing ≤40 kg: Paxlovid is not currently recommended
Eligibility Criteria
- Paxlovid is authorized for use in patients aged ≥12 years weighing at least 40 kg 2
- Treatment should be initiated as early as possible in the course of COVID-19 disease, ideally within 5 days of symptom onset 1
- The patient should have mild-to-moderate COVID-19 and be at high risk for progression to severe disease
Renal Considerations
If the 12-year-old patient has renal impairment, dosage adjustments are required:
- For moderate renal impairment (eGFR 30-59 mL/min): Reduce to 150 mg nirmatrelvir with 100 mg ritonavir twice daily for 5 days 1, 3
- For severe renal impairment (eGFR <30 mL/min): Paxlovid is not recommended 4
Important Clinical Considerations
Drug Interactions
Ritonavir is a potent CYP3A inhibitor that can cause significant drug-drug interactions. Before prescribing:
- Conduct a thorough medication review
- Use resources like the Liverpool COVID-19 Drug Interaction Tool to check for potential interactions 4
- Consider temporary discontinuation of certain medications during the 5-day treatment course if necessary
Administration Instructions
- Paxlovid should be taken twice daily, approximately 12 hours apart
- Can be taken with or without food
- All three tablets (two nirmatrelvir and one ritonavir) should be taken together
- The full 5-day course should be completed even if symptoms improve 1
Common Side Effects
- Dysgeusia (altered taste) - occurs in approximately 5.6% of patients 1, 5
- Diarrhea - occurs in approximately 3.1% of patients 1, 5
- Monitor for signs of adverse reactions, though the overall safety profile is favorable
Follow-up Recommendations
- Monitor for symptom improvement
- Watch for potential drug interactions that may manifest after completing the course of Paxlovid
- Be aware that some drug interactions may persist for several days after completing Paxlovid due to the prolonged effect of ritonavir on drug metabolism 1
Clinical Pitfalls to Avoid
- Failing to check for drug-drug interactions before prescribing
- Not adjusting the dose for renal impairment
- Discontinuing treatment prematurely when symptoms improve
- Prescribing to patients weighing less than 40 kg, for whom the medication is not currently authorized
Remember that Paxlovid must be started within 5 days of symptom onset for maximum effectiveness, with earlier initiation providing better outcomes.