Merck COVID-19 Treatment Pill: What You Need to Know

Merck's antiviral medication for COVID-19; an array of red pills with the Merck logo and the number 82 on them.


Key Takeaways

  • The Food and Drug Administration (FDA) authorized a second antiviral pill to treat COVID-19.
  • The pill, developed by Merck, is called molnupiravir. It is already authorized in the United Kingdom.
  • Molnupiravir was found to be at least 30% more effective than a placebo at preventing hospitalizations and death from COVID.
  • Experts want the public to know that the pill is not a substitute for vaccination, which still offers the greatest protection against COVID.

The Food and Drug Administration (FDA) has authorized an antiviral pill manufactured by Merck and Ridgeback Therapeutics to treat COVID-19.

The drug, called molnupiravir, is authorized to treat mild to moderate COVID-19 in adults with a positive SARS-CoV-2 test who are at high risk for progressing to severe illness and/or hospitalization. It is available via prescription only.

According Patrizia Cavazzoni, MD, director of the FDA’s Center for Drug Evaluation and Research, "Molnupiravir is limited to situations where other FDA-authorized treatments for COVID-19 are inaccessible or are not clinically appropriate."

The other available antiviral treatment, a pill from Pfizer called Paxlovid, was authorized the day prior. Paxlovid's authorization extends to people age 12 and up, while molnupiravir is not authorized for use in patients younger than 18 because of potential implications for bone and cartilage growth.

Who Is At High Risk for Severe COVID-19?

According to the Centers for Disease Control and Prevention (CDC), conditions and factors that may place someone at high risk for severe COVID include, but are not limited to:

  • Cancer
  • Chronic kidney disease
  • Chronic liver disease
  • Chronic lung disease
  • Dementia or other neurological conditions
  • Diabetes
  • Down syndrome
  • Heart conditions
  • HIV
  • Immunocompromised state
  • Mental health conditions
  • Obesity
  • Pregnancy
  • Sickle cell disease
  • Smoking
  • Organ transplant recipient
  • Stroke
  • Substance abuse disorders
  • Tuberculosis

What Is Molnupiravir?

Molnupiravir, which has already received authorization in the United Kingdom, is given as a pill. Its route of administration is an advantage over the currently available COVID-19 antiviral treatments, monoclonal antibodies, which must be given as an infusion at a doctor’s office, infusion center, or hospital.

Data on the drug has shown that it is most effective when taken within five days of COVID symptoms starting; however, that means its effectiveness relies on people getting tested for COVID promptly and getting the results back within the specified time frame for starting treatment.


According to the FDA, molnupiravir is administered as four 200 milligram capsules taken orally every 12 hours for five days. The total regimen consists of 40 tablets, and is not authorized for use beyond five consecutive days. 


Members of a November advisory committee to the FDA posed several questions about the safety and effectiveness of the new drug. Among the concerns were that during the company’s presentation to the advisory committee, it reported that the effectiveness of the drug had fallen from earlier projections that were released.

Will People Take a COVID Pill?

Even if a new COVID treatment becomes available, it can only help if people take it—and the people with the greatest need for treatment might be the least likely to accept it.

People who are unvaccinated are more likely to get COVID and become seriously ill if they do. While they would stand to benefit from new antivirals, surveys have indicated that many of them would not be willing to take a COVID pill if they were offered it.


On October 1, Merck announced early clinical trial results for the drug stating that it reduced hospitalization and death in people at risk for severe COVID disease by 50%.

However, when data was compiled for the full length of the trial, the reduction of hospitalization and death had fallen to 30%, according to data that was presented in the days before the meeting, at the meeting, and in a press release that Merck issued after the advisory committee’s decision. 


Other concerns that were raised during the advisory committee meeting were about how the drug works, and whether there are potential safety concerns that have not been thoroughly studied as of yet.

Molnupiravir keeps the COVID virus from replicating its genetic material. The committee questioned whether it would have the potential to damage DNA. Specifically, the concern is that there would be a risk to a developing fetus if a pregnant person or person with the potential to become pregnant took the drug.

Scientists for both companies and the FDA said that they thought that this outcome would be unlikely because the drug is only taken for a relatively short time (five days).

What Experts Think

Andrew Pavia, MD, chief of pediatric infectious diseases at the University of Utah, is not a member of the committee but he told Verywell that he thinks that “the data presented at the FDA advisory meeting and the discussion around it provide a complicated picture.”

Andrew Pavia, MD

The need to make rapid decisions on badly needed tools to fight the pandemic means we make decisions on what can be an incomplete picture of the benefits and risks.

— Andrew Pavia, MD

Pavia said that molnupiravir might not be as effective as first thought, but it probably has some benefit for high-risk patients.

“The difference between the efficacy during the first portion of the study and the second could not be adequately explained,” said Pavia. “While the safety data from the trial was good, there are lingering questions about the safety in groups that are particularly vulnerable to the potential effects of mutations, such as pregnant women and young children.”

Members of the advisory committee, as well as other infectious disease experts, noted the urgent need for more drugs to treat COVID.

“Normally we would wait for more data,” said Pavia. “But the need to make rapid decisions on badly needed tools to fight the pandemic means we make decisions on what can be an incomplete picture of the benefits and risks.”

Pfizer's COVID Pill

While Pfizer’s antiviral appears to be more effective than Merck’s (and potentially more helpful than monoclonal antibodies) it also has downsides: for one, the pill must be given with another medicine called ritonavir (an antiviral used to treat HIV) that interacts with many medications.

Amesh Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore, told Verywell that “oral antivirals that can prevent hospitalization are very valuable” and that even though Merck’s drug “isn’t a blockbuster and there are some toxicity concerns,” it will “have a role and help augment the toolbox that we use for COVID-19.”

Testing and Vaccination Still Matter

Experts want the public to understand that even though treatments are now authorized to treat COVID-19, it does not mean that COVID vaccination is no longer needed.

Aaron Glatt, MD, chief of infectious diseases at Mount Sinai South Nassau Hospital, told Verywell that the availability of a new drug would not mean that it will be used “instead of” a COVID vaccine, and that “vaccination remains critical to solving the COVID-19 pandemic.”

Testing for COVID is also an important way to prevent the spread of the virus because it identifies contagious people quickly and allows them to be isolated from others as soon as possible.

What About Omicron?

Adalja said the Merck drug may “get a bigger role” because of the Omicron variant—which is now the dominant strain in the United States—and that “some of the mutations present in the new variant have been associated with decreased efficacy of some of the monoclonal antibodies.”

“Even vaccinated people can have a breakthrough infection,’ said Glatt. “It is critically important that the government, industry, and private entrepreneurs continue to work together to expand, improve and increase the availability of easy to perform rapid testing.”

Pavia said that all current and potential COVID treatments rely on testing—monoclonal antibodies, molnupiravir, and the Paxlovid each have a narrow window early in infection where they can be beneficial.

“That means that patients who are at increased risk of complications need to seek testing early and get an answer within a day,” said Pavia. “Many have become reluctant to get tested, and testing can be difficult to access. The U.S. still has a long way to go to improve testing.”

What This Means For You

The FDA has authorized a second antiviral pill to treat COVID-19. The drug is most effective when taken within 5 days of symptom onset, which means that you’ll need to report symptoms to your doctor, get tested, get your test results, obtain a prescription quickly.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

By Fran Kritz
Fran Kritz is a freelance healthcare reporter with a focus on consumer health and health policy. She is a former staff writer for Forbes Magazine and U.S. News and World Report.