Standard Paxlovid Dosing for Normal Renal Function
For a patient with normal kidney function, prescribe Paxlovid as nirmatrelvir 300 mg (two 150 mg tablets) with ritonavir 100 mg (one 100 mg tablet), all three tablets taken together by mouth twice daily for 5 days. 1, 2
Prescription Details
What to write:
- Drug: Paxlovid (nirmatrelvir 300 mg/ritonavir 100 mg)
- Sig: Take 3 tablets (two 150 mg nirmatrelvir tablets + one 100 mg ritonavir tablet) by mouth twice daily for 5 days
- Quantity: 30 tablets total (enough for 5-day course)
- Timing: Administer approximately 12 hours apart (e.g., morning and evening)
Key Administration Points
Timing is critical: Initiate treatment as soon as possible after COVID-19 diagnosis and within 5 days of symptom onset, even if symptoms are mild 1, 2. The WHO guideline reinforces this, recommending administration as early as possible in the disease course 3.
Food flexibility: Tablets can be taken with or without food 2. Tablets must be swallowed whole—do not chew, break, or crush 2.
Complete the course: Patients must complete the full 5-day treatment course to maximize viral clearance and minimize SARS-CoV-2 transmission 2.
Critical Prescribing Considerations
Renal function verification: Before prescribing the standard dose, confirm the patient has normal renal function (eGFR ≥60 mL/min). No dose adjustment is needed for mild renal impairment (eGFR 60-89 mL/min) 1, 2.
Drug interactions: Ritonavir is a potent CYP3A4 inhibitor and causes numerous drug-drug interactions 3. Always check the Liverpool COVID-19 drug interaction tool before prescribing 3. Certain medications are contraindicated with Paxlovid, and others require dose adjustment or temporary discontinuation.
Common Pitfalls to Avoid
- Don't prescribe without checking drug interactions: This is the most common and dangerous error. Ritonavir interactions can be serious or life-threatening 2.
- Don't delay initiation: Efficacy depends on starting within 5 days of symptom onset 1, 2.
- Don't forget to specify both components: The prescription must clearly indicate both nirmatrelvir AND ritonavir doses 2.
- Don't assume all patients can take standard dosing: Always verify renal function first, as moderate renal impairment (eGFR 30-59 mL/min) requires dose reduction to 150 mg/100 mg twice daily 1, 2.
Missed Dose Instructions
If a dose is missed within 8 hours of the scheduled time, take it immediately and resume the normal schedule. If more than 8 hours have passed, skip the missed dose and take the next dose at the regularly scheduled time—never double up 2.