The Food and Drug Administration on Thursday authorized Merck's antiviral pill to treat Covid-19 for emergency use, adding another tool in the nation's arsenal to combat the virus.
The FDA's move comes a day after it authorized another antiviral drug, from Pfizer. Merck's treatment, known as molnupiravir and developed in partnership with Ridgeback Biotherapeutics, is cleared for use in adults with mild to moderate Covid who are at risk for severe disease, the agency said in a statement. Pfizer's pill was authorized for people as young as 12.
The use of molnupiravir will be limited to situations where other authorized treatments are inaccessible or not "clinically appropriate," Dr. Patrizia Cavazzoni, director of the FDA's Center for Drug Evaluation and Research, said in a 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 big advantage of oral treatments, like Merck's and Pfizer's, is that they can be taken at home, and don't require an IV or injection. That could help the nation's hospitals as new infections are expected to continue to surge this winter.
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Clinical trials found that the treatment reduced the risk of hospitalization and death among high-risk Covid patients by 30 percent.
By comparison, Pfizer's drug has been shown to be 89 percent effective at preventing high-risk people from being hospitalized or dying from Covid. Availability of Pfizer's treatment will initially be much more limited than Merck's. That may pose a dilemma for physicians over which treatment option to recommend to their patients.
The United States has agreed to purchase about 3.1 million courses of Merck's drug for $2.2 billion. Jeff Zients, the White House Covid-19 response coordinator, said at a briefing Wednesday that, if authorized, the majority of those treatment courses could be available to states and jurisdictions by the end of January.
Merck said in a statement Thursday that it is ready to ship "hundreds of thousands" of courses within days and 1 million courses over the next few weeks in the U.S.
An FDA advisory committee last month voted narrowly in favor of recommending the treatment. The close vote reflected concerns committee members had about both the effectiveness and the safety of the drug, including the potential risk to pregnant women and their fetuses.
The FDA recommended that patients use contraception while using Merck's treatment and for four days after the last dose.
The agency said molnupiravir is not authorized for use in patients under age 18 because the medication may affect bone and cartilage growth.
Potential side effects of the drug include diarrhea, nausea and dizziness, according to the agency.
During a presentation to the advisory committee on Nov. 30, Merck's scientists said they expect the drug will work against the omicron variant, now the dominant variant in the U.S. That's because the strain contains similar mutations to other versions of the virus, though further testing is still needed, the company said at the time.
A full course of Merck's treatment is a total of 40 pills, taken as four 200-milligram pills, twice a day for five days. Patients should begin the treatment within five days of the onset of symptoms. During the November advisory committee meeting, the drugmaker emphasized the importance of patients finishing the entire course of treatment as prescribed.