What is the recommended dose of Paxlovid (nirmatrelvir/ritonavir) for a 13-year-old patient?

Paxlovid Dosing for a 13-Year-Old Patient

Paxlovid (nirmatrelvir/ritonavir) is not currently approved for use in patients under 12 years of age, but for a 13-year-old patient who weighs at least 40 kg, the recommended dose is 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet) taken together orally twice daily for 5 days.

Age and Weight Considerations

The dosing of Paxlovid depends primarily on two factors:

1. Age requirement: Paxlovid is authorized for use in individuals 12 years of age and older 1
2. Weight requirement: Patient must weigh at least 40 kg (88 lbs) 1

For a 13-year-old patient who meets the weight requirement (≥40 kg), the standard adult dosing applies:

• Nirmatrelvir 300 mg (two 150 mg tablets) plus ritonavir 100 mg (one 100 mg tablet) taken together twice daily for 5 days

Renal Function Considerations

While standard dosing applies to patients with normal renal function or mild impairment, dose adjustment is necessary for moderate renal impairment:

• Normal renal function or mild impairment (eGFR ≥60 mL/min): Standard dose as above
• Moderate renal impairment (eGFR 30-59 mL/min): Reduced dose of nirmatrelvir 150 mg (one tablet) with ritonavir 100 mg twice daily 2
• Severe renal impairment (eGFR <30 mL/min): Not recommended

Drug Interaction Considerations

Ritonavir is a potent CYP3A4 inhibitor that can significantly affect the metabolism of many medications. Before prescribing Paxlovid to a 13-year-old:

• Review all current medications, including over-the-counter drugs and supplements
• Pay particular attention to medications metabolized by CYP3A4
• Consider temporary discontinuation or dose adjustment of interacting medications during the 5-day Paxlovid course 3

Clinical Efficacy and Timing

For maximum effectiveness:

• Treatment must be initiated within 5 days of symptom onset 1
• The complete 5-day course should be completed even if symptoms improve
• Paxlovid has been shown to reduce hospitalization risk by approximately 39% and death risk by 61% 4

Common Pitfalls and Caveats

1. Weight verification: Always confirm the patient weighs ≥40 kg before prescribing
2. Medication reconciliation: Carefully review all medications for potential interactions
3. Timing of initiation: Efficacy decreases significantly if started beyond 5 days of symptom onset
4. Taste disturbance: Dysgeusia (altered taste) is a common side effect that patients should be informed about
5. Rebound symptoms: Some patients may experience symptom recurrence after completing treatment; this does not typically require additional treatment

By following these guidelines, Paxlovid can be appropriately dosed for a 13-year-old patient who meets the weight requirement, potentially reducing their risk of COVID-19 progression to severe disease.