Paxlovid (Nirmatrelvir/Ritonavir): Uses, Safety and Interactions

What Paxlovid is

Paxlovid contains separate nirmatrelvir 150 mg tablets and ritonavir 100 mg tablets in one treatment pack. Ritonavir slows the metabolism of nirmatrelvir. This overview follows the US prescribing information revised in February 2026; eligibility and authorisations elsewhere may differ. The US approved indication is mild-to-moderate COVID-19 in adults at high risk of progression to severe illness. It is not approved as pre-exposure or post-exposure prevention.

Why prompt assessment matters

Outpatient antiviral treatment has a short starting window. CDC guidance recommends assessing higher-risk patients quickly, considering factors such as age, immune compromise and underlying illness. Paxlovid is started within five days of symptom onset under the cited US label. This page cannot establish whether an individual needs antiviral treatment or whether another option is preferable. Severe or worsening illness needs appropriate medical assessment rather than waiting for an online medicine comparison.

Interactions and kidney function

Ritonavir strongly inhibits CYP3A, so interactions can cause severe toxicity or loss of antiviral activity. Simvastatin, lovastatin, carbamazepine, rifampin and St. John's wort are important examples requiring specific label-based management. Tacrolimus and ciclosporin demand expert assessment and close monitoring when coadministration is considered. A clinician must review all medicines, including recent treatment and supplements; simply stopping a strong enzyme inducer does not immediately remove its effect. The current US label includes adjusted regimens for moderate and severe kidney impairment, including haemodialysis. Severe renal impairment is therefore not a blanket contraindication in that label. The US label does not recommend use in severe liver impairment.

Adverse effects and personal questions

Altered taste and diarrhoea are common adverse effects. Urgent help is needed for serious allergic symptoms or a blistering rash. Liver disease, pregnancy, breastfeeding and hormonal contraception should be raised with the prescriber. Unrecognised or uncontrolled HIV-1 infection also needs assessment because ritonavir can promote HIV protease-inhibitor resistance. Do not change anticoagulants, transplant treatment or other essential medicines yourself to make Paxlovid possible. The pack strength is not an individual dose recommendation.

Sources

• Pfizer: Paxlovid — US prescribing information — US prescribing information revised February 2026
• CDC: COVID-19 treatment clinical care for outpatients — Guidance dated 8 October 2026; eligibility and early-assessment context only

Source check: 30 October 2026. This records a source check, not a clinical review by a doctor or pharmacist. Follow the leaflet for the exact product supplied to you.