How does Paxlovid treat COVID-19?
Michael Ganio, PharmD
Paxlovid (Pfizer) is a combination of two oral antiviral medications: nirmatrelvir and ritonavir. Nirmatrelvir is a protease inhibitor that prevents viral replication. Ritonavir is used to boost the levels of nirmatrelvir by slowing its hepatic metabolism. Paxlovid has received emergency authorization for use in adults and children aged 12 years or older (and who weigh at least 88 lb) who have tested positive for COVID-19 and are at high risk for severe disease.
Paxlovid must be started within 5 days of symptom onset.
How is Paxlovid prescribed?
Paxlovid is available in two packaging configurations, with different doses of nirmatrelvir, depending on patient renal function.
Most patients (those with normal renal function or mild renal impairment (estimated glomerular filtration rate [eGFR] ≥ 60 mL/min) should be prescribed the 300 mg nirmatrelvir/100 mg ritonavir dose pack.
Patients with moderate renal impairment (eGFR ≥ 30 to < 60 mL/min) should be prescribed the 150 mg nirmatrelvir/ 100 mg ritonavir dose pack. Paxlovid is not recommended in patients with severe renal impairment (< 30 mL/min).
Paxlovid is taken twice daily for 5 days. Prescriptions should specify the numeric dose of each active ingredient within Paxlovid and also specify that completion of the full 5-day treatment course and continued isolation in accordance with public health recommendations are important to maximize viral clearance and minimize transmission of SARS-CoV-2.
