Paxlovid Ordering for Adults with Normal Renal Function
For an adult with normal renal function (eGFR ≥60 mL/min), order Paxlovid as: nirmatrelvir 300 mg (two 150 mg tablets) with ritonavir 100 mg (one 100 mg tablet), all three tablets taken together orally twice daily for 5 days. 1
Specific Ordering Instructions
Write the prescription as follows:
- Nirmatrelvir 150 mg tablets: Take 2 tablets by mouth twice daily (morning and bedtime) for 5 days 1
- Ritonavir 100 mg tablets: Take 1 tablet by mouth twice daily (morning and bedtime) for 5 days 1
- All 3 tablets must be taken together at the same time 1
Critical Timing and Administration Details
- Initiate treatment as soon as possible after COVID-19 diagnosis and within 5 days of symptom onset 1
- Administer at approximately the same time each day (morning and bedtime dosing) 1
- Can be taken with or without food 1
- Tablets should be swallowed whole—do not chew, break, or crush 1
- Complete the full 5-day course even if symptoms improve 1
Mandatory Pre-Prescribing Drug Interaction Review
Before writing any Paxlovid prescription, you must review all patient medications for potentially dangerous interactions 2, 3, 1. Ritonavir is a strong CYP3A inhibitor that can cause severe, life-threatening, or fatal drug interactions 1.
High-Risk Medications to Avoid or Adjust:
Contraindicated medications (do not prescribe Paxlovid if patient is taking):
- Antiarrhythmics: amiodarone, flecainide, propafenone 2
- Statins: lovastatin, simvastatin 2
- Anticoagulants: rivaroxaban (high bleeding risk) 2
Medications requiring dose adjustment or temporary hold:
- Atorvastatin: Hold during treatment or reduce dose significantly; monitor for myopathy symptoms 2
- Immunosuppressants: Tacrolimus should be discontinued or given as microdose on day 1; cyclosporine reduced to 20% of initial dose; mTOR inhibitors require adjustment 4
- Use the Liverpool COVID-19 Drug Interaction Tool before prescribing 2, 3
Missed Dose Instructions
- If missed within 8 hours of scheduled time: Take as soon as possible and resume normal schedule 1
- If missed by more than 8 hours: Skip the missed dose, take next dose at regularly scheduled time 1
- Never double the dose 1
Common Pitfalls to Avoid
- Failing to verify renal function before prescribing—always confirm eGFR ≥60 mL/min for standard dosing 1
- Not reviewing drug interactions—this is the most critical safety concern with Paxlovid 1
- Prescribing nirmatrelvir without ritonavir—nirmatrelvir must be co-administered with ritonavir or therapeutic levels will not be achieved 1
- Interaction risk extends beyond the 5-day treatment period due to ritonavir's effects on drug metabolism 2, 3