Merck’s Covid Pill Is Authorized for High-Risk Adults

The Food and Drug Administration on Thursday authorized a second antiviral pill for Covid but said it should not be preferred over other treatments.

The F.D.A. cleared the pill, developed by Merck and known as molnupiravir, for adults who are vulnerable to becoming severely ill from Covid and for whom alternative treatment options are “not accessible or clinically appropriate.”

The agency’s decision reflects concerns that Merck’s pill is only modestly effective and carries possible safety risks, including for pregnant women.

Merck’s treatment is expected to be available early next month. With the Omicron variant driving an onslaught of infections, the drug will be in greater supply in the coming weeks than other treatments in the United States.

Older people and those who have conditions like obesity, diabetes or heart disease would be eligible to get a prescription for Merck’s pills if they become sick from the coronavirus and cannot get treatments like Pfizer’s newly authorized pills or monoclonal antibody drugs. Both vaccinated and unvaccinated people will be eligible.

But while the agency authorized Pfizer’s treatment for high-risk Covid patients as young as 12, it said that it was authorizing Merck’s drug only for adults because it “may affect bone and cartilage growth.”

Even before the F.D.A.’s decision, some doctors and health officials had tempered expectations for Merck’s drug. It appears far less effective than a similar pill from Pfizer, which received F.D.A. authorization on Wednesday and is expected to become more widely available in the United States starting in a few months.

In a key clinical trial, Merck’s drug reduced the risk of hospitalization or death by 30 percent when given to high-risk, unvaccinated people within five days of the onset of symptoms. Pfizer’s pill was found to reduce that risk by 88 percent.