What It's Used For

COVID-19 treatment in high-risk adults
Prevention of COVID-19 hospitalization
Prevention of COVID-19 death
Treatment of mild-to-moderate COVID-19 in eligible patients

Side Effects

Common Side Effects:

Altered taste (dysgeusia) - metallic or bitter taste
Diarrhea
High blood pressure
Muscle aches
Nausea
Abdominal pain

Serious Side Effects (seek immediate medical attention):

Severe allergic reactions (rash, swelling, difficulty breathing)
Liver problems (yellowing of skin/eyes, dark urine)
Drug interactions causing serious adverse effects
Worsening COVID-19 symptoms

Additional Information

Paxlovid is an oral antiviral medication for treatment of mild-to-moderate COVID-19 in adults at high risk for progression to severe disease. It contains two medications: nirmatrelvir, which inhibits viral replication, and ritonavir, which boosts nirmatrelvir levels.

How Paxlovid Works

Nirmatrelvir is a SARS-CoV-2 main protease (Mpro) inhibitor. This protease is essential for viral replication, and blocking it prevents the virus from making functional proteins needed to reproduce. Ritonavir inhibits CYP3A4, slowing nirmatrelvir metabolism and keeping blood levels elevated for longer.

Composition and Dosing

Each dose consists of two nirmatrelvir 150 mg tablets plus one ritonavir 100 mg tablet, taken together twice daily for 5 days. Treatment should begin within 5 days of symptom onset. The medication comes in convenient daily dose packs.

Eligibility and Indications

Paxlovid is indicated for adults with positive COVID-19 test results who are at high risk for progression to severe disease. Risk factors include age 65+, obesity, diabetes, heart disease, lung disease, immunocompromising conditions, and others. It is not authorized for pre-exposure or post-exposure prevention.

Efficacy

Clinical trials showed Paxlovid reduced risk of hospitalization and death by approximately 89% when started within 5 days of symptoms in high-risk unvaccinated patients. Real-world data suggests continued effectiveness, though benefit may be less pronounced in vaccinated individuals.

Important Drug Interactions

Ritonavir is a potent CYP3A4 inhibitor, causing numerous significant drug interactions. Many medications are contraindicated including certain statins (lovastatin, simvastatin), sedatives (midazolam, triazolam), certain heart medications, and others. A thorough medication review is essential before prescribing.

Rebound Phenomenon

Some patients experience COVID-19 symptom rebound after completing Paxlovid treatment, with return of symptoms and positive tests. This typically occurs 2-8 days after initial recovery. The clinical significance and management of rebound is still being studied.

Special Populations

Dose adjustment is required for moderate renal impairment (eGFR 30-60 mL/min): nirmatrelvir is reduced to 150 mg with ritonavir 100 mg twice daily. Paxlovid is not recommended for severe renal or hepatic impairment. Safety during pregnancy has not been established.

Contraindications

Paxlovid is contraindicated in patients taking medications highly dependent on CYP3A for clearance where elevated levels could cause serious reactions. This includes certain medications for arrhythmias, seizures, and psychiatric conditions. Complete medication reconciliation is essential.

Access and Availability

Paxlovid is available by prescription at pharmacies. It transitioned from emergency use authorization to full FDA approval in May 2023 for adults and remains under EUA for pediatric patients 12 years and older weighing at least 40 kg.

Learn more at MedlinePlus

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Paxlovid