A new treatment for COVID-19 has become available as the U.S. now faces yet another rise in coronavirus (SARS-CoV-2) cases due to the surging Omicron variant. The U.S. Food and Drug Administration (FDA) announced its emergency use authorization (EUA) of Pfizer’s Paxlovid, the first oral antiviral treatment for COVID-19 in pill form.

What Is Paxlovid?

Paxlovid consists of three tablets taken by mouth twice daily for five consecutive days: nirmatrelvir (two tablets) and ritonavir (one tablet).

• Nirmatrelvir blocks a protein that prevents the coronavirus from reproducing.
• Ritonavir slows nirmatrelvir’s decomposition in the body to extend its effectiveness. 

Treatment with Paxlovid is intended for mild-to-moderate COVID-19 (coronavirus disease) in adults and children 12 years of age and up who weigh at least 88 pounds. 

• Available by prescription only, the drug is meant for those who test positive for coronavirus and are vulnerable to severe COVID-19. 
• People are instructed to start Paxlovid as soon after diagnosis as possible and within five days of showing symptoms.
• Paxlovid is not a substitute for vaccination against COVID-19 or a preventative measure before or after exposure to the virus, and it is not designed for those needing hospitalization for severe COVID-19.

The FDA reminds readers that an EUA is not the same as an approval. But when deciding on an EUA, the agency reviews the entire body of available evidence and carefully weighs the known and potential benefits with known and potential harms. “It is reasonable to believe that Paxlovid may be effective for the treatment of mild-to-moderate COVID-19 in authorized patients,” states the FDA. When used as directed, they’ve concluded that Paxlovid’s known and potential benefits outweigh its known and potential risks.

Supportive Research

The FDA based their decision primarily on data from EPIC-HR, a randomized, controlled, double-blind trial that looked at the effects of Paxlovid in symptomatic, non-hospitalized people with confirmed COVID-19.

• 1,039 people with COVID-19 given Paxlovid were compared to 1,049 people with COVID-19 given a placebo.
• Adults aged 18-59 years who were at risk for severe illness and those 60 years and older, regardless of risk factors, were studied.
• No patient had been vaccinated against COVID-19 or had been previously infected, and no monoclonal antibody therapy was used.
• Patients were given Paxlovid or a placebo within five days of experiencing symptoms, as advised, and were followed for 28 days.

The researchers found an 88% decline in COVID-19 hospitalization and all-cause death with Paxlovid versus placebo, with 0.8% of Paxlovid recipients being hospitalized or dying versus 6% of placebo recipients.

Possible Side Effects

Research into Paxlovid’s effectiveness and safety for COVID-19 continues, but possible side effects include diarrhea, impaired taste, muscle aches, liver damage, and elevated blood pressure. The drug is not recommended for people with severe kidney or liver issues, and a reduced dose is required for those with moderate kidney impairment. 

Paxlovid can also interfere with certain drugs. For example, Paxlovid can lead to HIV-1 drug resistance in people with unmanaged or undiagnosed HIV-1 infection. Because it prevents the enzymatic breakdown of certain medications, Paxlovid should also not be taken with drugs that rely on those enzymes for metabolism, where elevated levels of those drugs could cause serious harm.

‘A Major Step Forward’

Patrizia Cavazzoni, director of the FDA’s Center for Drug Evaluation and Research, stated of the authorization for Paxlovid:

“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. 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.”

For More Information

The FDA has provided fact sheets to healthcare professionals and patients and caregivers discussing Paxlovid dosing, possible side effects, drug interactions, and who can prescribe the drug. For questions concerning Paxlovid for COVID-19, visit the FDA’s frequently asked questions page.

Shortly after announcing the EUA of Paxlovid, the FDA announced the same authorization of Merck’s molnupiravir, a second antiviral pill for COVID-19. You can learn more about that drug in the FDA’s December 23, 2021 press release.

Much about the novel coronavirus, i.e., COVID-19, is still not fully understood. As research progresses and our knowledge of the virus increases, information can change rapidly. We strive to update all of our articles as quickly as possible, but there may occasionally be some lag between scientific developments and our revisions. 

*U.S. Food and Drug Administration. (2021, December 22). Coronavirus (COVID-19) Update: FDA Authorizes First Oral Antiviral for Treatment of COVID-19 [Press release]. https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-first-oral-antiviral-treatment-covid-19