The U.S. Food and Drug Administration issued an emergency use authorization on Dec. 22 for Pfizer’s COVID-19 treatment pill and on Dec. 23 for Merck’s molnupiravir to treat to mild-to-moderate COVID-19.
“Today’s authorization introduces the first treatment for COVID-19 that is in the form of a pill that is taken orally — a major step forward in the fight against this global pandemic,” said Patrizia Cavazzoni, director of the FDA’s Center for Drug Evaluation and Research, in a press release on Dec. 22. “This authorization provides a new tool to combat COVID-19 at a crucial time in the pandemic as new variants emerge and promises to make antiviral treatment more accessible to patients who are at high risk for progression to severe COVID-19.”
Pfizer's pill — Paxlovid — is authorized to treat COVID-19 in adults and pediatric patients who are 12 years of age and older weighing at least 40 kilograms or about 88 pounds with positive results of direct SARS-CoV-2 testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death.
Paxlovid is available by prescription only and should be initiated as soon as possible after diagnosis of COVID-19 and within five days of symptom onset.
Paxlovid is not authorized for the pre-exposure or post-exposure prevention of COVID-19 or for initiation of treatment in those requiring hospitalization due to severe or critical COVID-19. Paxlovid is not a substitute for vaccination in individuals for whom COVID-19 vaccination and a booster dose are recommended, the FDA stated.
Merck’s molnupiravir is authorized for the treatment of mild-to-moderate coronavirus disease (COVID-19) in adults with positive results of direct SARS-CoV-2 viral testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death, and for whom alternative COVID-19 treatment options authorized by the FDA are not accessible or clinically appropriate.
Molnupiravir is not authorized for use in patients younger than 18 years of age because molnupiravir may affect bone and cartilage growth nor for the pre-exposure or post-exposure prevention of COVID-19 or for initiation of treatment in patients hospitalized due to COVID-19 because benefit of treatment has not been observed in people when treatment started after hospitalization due to COVID-19.
The FDA has approved one vaccine and authorized others to prevent COVID-19 and serious clinical outcomes associated with a COVID-19 infection, including hospitalization and death. The FDA urges the public to get vaccinated and receive a booster if eligible.
Paxlovid consists of nirmatrelvir, which inhibits a SARS-CoV-2 protein to stop the virus from replicating, and ritonavir, which slows down nirmatrelvir’s breakdown to help it remain in the body for a longer period at higher concentrations. Paxlovid is administered as three tablets (two tablets of nirmatrelvir and one tablet of ritonavir) taken together orally twice daily for five days, for a total of 30 tablets. Paxlovid is not authorized for use for longer than five consecutive days.
Molnupiravir is a medication that works by introducing errors into the SARS-CoV-2 virus’ genetic code, which prevents the virus from further replicating. Molnupiravir is administered as four 200 milligram capsules taken orally every 12 hours for five days, for a total of 40 capsules. Molnupiravir is not authorized for use for longer than five consecutive days.
The issuance of an EUA is different than an FDA approval. In determining whether to issue an EUA, the FDA evaluates the totality of scientific evidence available and carefully balances any known or potential risks with any known or potential benefits of the product.
Based on the FDA’s review of the totality of the scientific evidence available, the agency has determined that it is reasonable to believe that Paxlovid may be effective for the treatment of mild-to-moderate COVID-19 in authorized patients. The agency has also determined that the known and potential benefits of Paxlovid, when used consistent with the terms and conditions of the authorization, outweigh the known and potential risks of the product. There are no adequate, approved and available alternatives to Paxlovid for the treatment of COVID-19.
The primary data supporting this EUA for Paxlovid are from EPIC-HR, a randomized, double-blind, placebo-controlled clinical trial studying Paxlovid for the treatment of non-hospitalized symptomatic adults with a laboratory confirmed diagnosis of SARS-CoV-2 infection. Patients were adults 18 years of age and older with a prespecified risk factor for progression to severe disease or were 60 years and older regardless of prespecified chronic medical conditions. All patients had not received a COVID-19 vaccine and had not been previously infected with COVID-19.
The main outcome measured in the trial was the proportion of people who were hospitalized due to COVID-19 or died due to any cause during 28 days of follow-up. Paxlovid significantly reduced the proportion of people with COVID-19 related hospitalization or death from any cause by 88 percent compared to placebo among patients treated within five days of symptom onset and who did not receive COVID-19 therapeutic monoclonal antibody treatment.
In this analysis, 1,039 patients had received Paxlovid, and 1,046 patients had received placebo and among these patients, 0.8 percent who received Paxlovid were hospitalized or died during 28 days of follow-up compared to 6 percent of the patients who received placebo. The safety and effectiveness of Paxlovid for the treatment of COVID-19 continue to be evaluated.
Possible side effects of Paxlovid include impaired sense of taste, diarrhea, high blood pressure and muscle aches. Using Paxlovid at the same time as certain other drugs may result in potentially significant drug interactions. Using Paxlovid in people with uncontrolled or undiagnosed HIV-1 infection may lead to HIV-1 drug resistance. Ritonavir may cause liver damage, so caution should be exercised when giving Paxlovid to patients with preexisting liver diseases, liver enzyme abnormalities or liver inflammation.
Because Paxlovid works, in part, by inhibiting a group of enzymes that break down certain drugs, Paxlovid is contraindicated with certain drugs that are highly dependent on those enzymes for metabolism and for which elevated concentrations of certain drugs are associated with serious and/or life-threatening reactions.
Paxlovid is also contraindicated with drugs that, conversely, strongly induce those same enzymes, leading to the faster breakdown of nirmatrelvir or ritonavir, as reduced concentrations of nirmatrelvir or ritonavir may be associated with potentially losing virologic response and developing viral resistance. Paxlovid cannot be started immediately after discontinuing such medications because the effects of those medications remain after discontinuation. For a complete list of drugs that should not be taken in combination with Paxlovid, see the fact sheet for healthcare providers.
Paxlovid is not recommended in patients with severe kidney or severe liver impairment. In patients with moderate renal impairment, a reduced Paxlovid dose is needed. Patients with kidney or liver problems should discuss with their healthcare provider whether Paxlovid is right for them.
The primary data supporting this EUA for molnupiravir are from MOVe-OUT, a randomized, double-blind, placebo-controlled clinical trial studying molnupiravir for the treatment of non-hospitalized patients with mild to moderate COVID-19 at high risk for progression to severe COVID-19 and/or hospitalization. Patients were adults 18 years of age and older with a prespecified chronic medical condition or at increased risk of SARS-CoV-2 infection for other reasons who had not received a COVID-19 vaccine. The main outcome measured in the trial was the percentage of people who were hospitalized or died due to any cause during 29 days of follow-up. Of the 709 people who received molnupiravir, 6.8% were hospitalized or died within this time period compared to 9.7 percent of the 699 people who received a placebo. Of the people who received molnupiravir one died during the follow-up period compared to nine people who received placebo. Side effects observed in the trial included diarrhea, nausea and dizziness. The safety and effectiveness of molnupiravir for the treatment of COVID-19 continue to be evaluated.
Based on findings from animal reproduction studies, molnupiravir may cause fetal harm when administered to pregnant individuals. Therefore, molnupiravir is not recommended for use during pregnancy. Molnupiravir is only authorized to be prescribed to a pregnant individual after the prescribing healthcare provider has determined that the benefits of being treated with molnupiravir would outweigh the risks for that individual patient and after the prescribing health care provider has communicated the known and potential benefits and the potential risks of using molnupiravir during pregnancy to the pregnant individual. Females of childbearing potential are advised to use a reliable method of birth control correctly and consistently during treatment with molnupiravir and for four days after the final dose. Males of reproductive potential who are sexually active with females of childbearing potential are advised to use a reliable method of birth control correctly and consistently during treatment with molnupiravir and for at least three months after the final dose. Questions and concerns about reliable birth control methods that are appropriate for use during treatment with molnupiravir, as well as how molnupiravir may affect sperm cells, should be directed at one’s healthcare provider.
Under the EUA, fact sheets that provide important information about using Paxlovid and molnupiravir in the treatment of COVID-19 as authorized must be made available to healthcare providers and to patients and caregivers. These fact sheets include dosing instructions, potential side effects, drug interactions and information about who is able to prescribe Paxlovid and molnupiravir.