What Is Molnupiravir? Uses, Dosage, and What You Need to Know in 2026

Molnupiravir (brand name: Lagevrio) is an oral antiviral medication used to treat COVID-19 in adults who are at high risk for serious illness. It's taken as a pill for just 5 days — making it one of the most convenient COVID-19 treatments available. But it is not the right medication for everyone, and understanding exactly when and how to use it matters.

This guide answers the most common patient questions about molnupiravir in plain language.

What Is Molnupiravir (Lagevrio)?

Molnupiravir is an antiviral medication made by Merck (in partnership with Ridgeback Biotherapeutics) and sold under the brand name Lagevrio. It is authorized in the United States under an FDA Emergency Use Authorization (EUA) — not a standard FDA approval — for the treatment of mild-to-moderate COVID-19 in certain adults.

It was invented at Emory University and originally developed to treat influenza before being repurposed for COVID-19. The UK was the first country to authorize it in November 2021; the FDA followed with its EUA in December 2021.

What Is Molnupiravir Used For?

Molnupiravir is authorized to treat mild-to-moderate COVID-19 caused by SARS-CoV-2 in adults who meet all of the following criteria:

18 years of age or older

Positive SARS-CoV-2 test result

At high risk for progression to severe disease (hospitalization or death)

For whom alternative COVID-19 treatments (Paxlovid, remdesivir) are not accessible or appropriate

Risk factors for severe COVID-19 include: being over 50 years old, obesity, diabetes, heart or lung disease, chronic kidney disease, immunocompromised states, and certain other chronic medical conditions.

Molnupiravir is NOT authorized for: prevention of COVID-19, treatment after hospitalization for COVID-19, or use in patients under 18.

How Effective Is Molnupiravir?

In the Phase 3 MOVe-OUT clinical trial, molnupiravir reduced the risk of hospitalization or death in high-risk, unvaccinated COVID-19 patients. Of patients who received molnupiravir, 6.8% were hospitalized or died within 29 days, compared to 9.7% who received placebo — a relative risk reduction of about 30%.

Compared to Paxlovid, molnupiravir is less effective — direct studies show Paxlovid clears the virus more rapidly. However, molnupiravir's key advantage is that it has no known drug-drug interactions, making it the preferred oral antiviral for patients on complex medication regimens.

What Is the Correct Molnupiravir Dosage?

The standard molnupiravir dosage is:

Dose: 800 mg (4 capsules × 200 mg each) taken by mouth every 12 hours

Duration: 5 days (total of 40 capsules)

Timing: Start as soon as possible after diagnosis and within 5 days of symptom onset

With food: Can be taken with or without food. If it causes stomach upset, try taking with food.

Renal/hepatic adjustments: None required for kidney or liver impairment

Always complete the full 5-day course — even if you feel better before finishing. Stopping early may allow the virus to rebound.

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Who Should NOT Take Molnupiravir?

Pregnant individuals (boxed warning: potential fetal harm)

People under 18 years of age (bone and cartilage toxicity risk)

People who have not tested positive for COVID-19 (not authorized for prophylaxis)

Patients already hospitalized primarily due to COVID-19 (benefit not demonstrated)

Is Molnupiravir a Controlled Substance?

No. Molnupiravir is not a DEA-scheduled controlled substance. It is available by prescription only, but there are no special prescribing restrictions related to controlled substance scheduling. Any licensed prescriber can write the prescription.

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How Much Does It Cost?

Retail cash price is approximately $1,042–$1,100 per 5-day course. However, most patients pay significantly less:

Commercially insured patients: use the Merck savings coupon to pay as little as $10

Medicare Part D: typically Tier 1 coverage with low copays

Uninsured: Merck Patient Assistance Program may provide it at no cost (merckhelps.com/LAGEVRIO)

Where Can You Get Molnupiravir?

Molnupiravir requires a prescription and is available at major pharmacy chains. Because it may not be in stock everywhere, use medfinder to locate a pharmacy near you that has it in stock. Read our full guide on how to find molnupiravir near you for more details.

For more on side effects, read our guide on Molnupiravir Side Effects: What to Expect and When to Call Your Doctor.