Merck applies for emergency authorization for what would be the first pill to treat Covid.

Merck said on Monday that it had submitted an application to the Food and Drug Administration to authorize what would be the first antiviral pill to treat Covid.

Clearance for the drug, molnupiravir, would be a milestone in the fight against the coronavirus, experts said, because a convenient, relatively inexpensive treatment could reach many more high-risk people sick with Covid than the cumbersome antibody treatments currently being used.

The Biden administration is preparing for an authorization that could come within weeks; the pill would likely to be allocated to states, as was the case with the vaccines. States could then distribute the pills how they wish, such as through pharmacies or doctors’ practices, senior administration officials said.

If the pill wins authorization, tens of millions of Americans will most likely be eligible to take it if they get sick with Covid — many more than the supply could cover, at least initially. The federal government has placed an advance order for enough pills for 1.7 million Americans, at a price of about $700 per patient. That is about one-third the price that the government is paying for the monoclonal antibody treatments, which are generally given via intravenous infusion.

Merck, which is developing the pill with Ridgeback Biotherapeutics of Miami, expects to be able to produce enough pills for 10 million people by the end of this year. Governments have raced to lock up supplies since the strong clinical trial results were released this month; Australia, Malaysia, Singapore and South Korea have all announced agreements.

An antiviral pill being developed by Pfizer and one from Atea Pharmaceuticals-Roche will report study results in the next months and, if effective, could expand supply.

Merck’s pill is meant to be taken at home as four capsules twice a day for five days, for a total of 40 pills. It halved hospitalizations and deaths in a clinical trial that enrolled unvaccinated adults who had begun showing Covid symptoms within the previous five days and were at high risk for bad outcomes from the disease.

Merck said it was seeking authorization for its pill to be given only to high-risk adults, which in the clinical trial was most commonly people over 60 or younger people with obesity, diabetes or heart disease.

It was not clear whether the treatment would be available to vaccinated people, who were not eligible for the clinical trial. A company spokeswoman said it would be up to the F.D.A. to decide.

Originally tested for influenza, the drug works by stopping the coronavirus from replicating by inserting errors into its genetic code.

That mechanism is likely to make one high-risk group, people who are pregnant, ineligible to receive the pills if they are authorized, because of fears that the drug might cause mutations that could result in birth defects. In the clinical trial, volunteers had to agree to abstain from unprotected sexual intercourse for four days after they finished taking the pills, and some women of childbearing age had to have a negative pregnancy test to enroll in the study.

Sheryl Gay Stolberg contributed reporting.