FDA Gives OK to Merck's Antiviral At-Home COVID Pill

The U.S. Food and Drug Administration on Thursday approved the emergency use of Merck's molnupiravir pill for the treatment of mild to moderate COVID in people who've just tested positive.

The approval comes on the heels of Wednesday's approval of Pfizer's COVID antiviral pill Paxlovid.

Both pills are intended only for people who at high risk for hospitalization and death from severe COVID, and they are available by prescription only.

"Today's authorization provides an additional treatment option against the COVID-19 virus in the form of a pill that can be taken orally," Dr. Patrizia Cavazzoni, director of the FDA's Center for Drug Evaluation and Research, said in an agency statement.

"As new variants of the virus continue to emerge, it is crucial to expand the country's arsenal of COVID-19 therapies using emergency use authorization, while continuing to generate additional data on their safety and effectiveness," she said.

The authorizations come as the United States plunges into a fresh surge of COVID, spurred on by the highly infectious Omicron variant.

But the two pills are not interchangeable: Pfizer’s drug far outperformed Merck’s in clinical trials. While molnupiravir cut the risk of hospitalization and death in high-risk patients by 30%, Paxlovid did so by nearly 90%.

Molnupiravir works by introducing errors into the coronavirus' genetic code, which first hampers and then prevents the virus from replicating.

"The copy machine for the virus becomes more sloppy," explained Jonathan Abraham, an assistant professor of microbiology at Harvard Medical School in Boston. "That eventually allows the virus to make so many mistakes that the virus is no longer functional."

COVID patients would take four 200-milligram capsules at a time every 12 hours for five days, for a total of 40 capsules, the FDA said.

As with Paxlovid, patients should start their pill regimen as soon as possible after their COVID diagnosis, and within five days of symptom onset, according to the FDA.

Molnupiravir is not authorized to be taken to prevent COVID infection in people who've been exposed to a sick person, the FDA noted. It also can't be taken by patients who are so sick that they've landed in the hospital.

The FDA warned that the two antiviral pills should not be considered a substitute for vaccination.

Molnupiravir's emergency approval was supported by a clinical trial comparing 709 COVID patients who got the drug to 699 patients who received a placebo.

About 6.8% of people who got molnupiravir were hospitalized or died during a month of follow-up, compared to 9.7% of people who received a placebo, the FDA said. That includes one patient given molnupiravir who died, compared with nine placebo patients who died.

Side effects observed in the clinical trial included diarrhea, nausea and dizziness.

Molnupiravir is not authorized for patients younger than 18 because it might affect bone and cartilage growth.

It's also not recommended for use during pregnancy, since animal studies showed that the drug may cause fetal harm. Molnupiravir can only be prescribed to a pregnant woman if her doctor feels that the benefits outweigh the risks and has outlined those risks to her.