FDA Authorizes Pfizer Antiviral Pill for COVID-19

Damian McNamara

December 22, 2021

Find the latest COVID-19 news and guidance in Medscape's  Coronavirus Resource Center.

The FDA on Wednesday granted emergency use authorization of a new antiviral pill to treat people with symptomatic COVID-19.

Pfizer's ritonavir plus nirmatrelvir (Paxlovid) can now be taken by patients aged 12 and up who weigh at least 88 pounds.

The antiviral is only for people who test positive for coronavirus, and who are at high risk for severe COVID-19, including hospitalization or death. It is available by prescription only and should be taken as soon as possible after diagnosis and within 5 days of the start of symptoms

Paxlovid is taken as three tablets taken together orally twice a day for 5 days, for a total of 30 tablets.

Possible side effects include reduced sense of taste (ageusia), diarrhea, high blood pressure, and muscle aches.

The authorization arrives as the US faces a surge in Omicron case numbers. Evidence points to waning effectiveness of some monoclonal antibody treatments as Americans struggle to maintain some sense of tradition and normalcy around the holidays.

Paxlovid joins remdesivir as available antivirals to treat COVID-19. Remdesivir is fully approved by the FDA but is only given intravenously in the hospital. 

The pill form of COVID-19 antivirals come with some obvious advantages — including greater convenience for consumers, including home use, and the potential to expand treatment for people in low- and middle-income countries.

"An Exciting Step Forward"

The emergency use authorization (EUA) for Pfizer's new drug has been highly anticipated, and news of its impending authorization circulated on social media on Tuesday. Eric Topol, MD, called the development an "exciting step forward." (Topol is editor-in-chief of Medscape.)

Topol and many others, however, also expected the FDA to grant emergency use authorization for an antiviral from Merck. There was no immediate word Wednesday if that was going to happen.


"The emergency use authorization today of Paxlovid (nirmatrelvir plus ritonavir) is a great step forward in our struggle against COVID-19," agreed Prathit Kulkarni, MD.

It is important to take the antiviral within 5 days of starting to have symptoms due to COVID-19, Kulkarni told Medscape Medical News when asked to comment.

In addition, "the highest benefit in preventing hospitalization or death was seen in patients who did not have evidence of prior immunity against SARS-CoV-2 through vaccination or prior infection. Benefit was also seen in younger and older patients, as well as folks with and without certain medical conditions," said Kulkarni, assistant professor of medicine in the section of infectious diseases at Baylor College of Medicine in Houston, Texas.

Paxlovid has the potential to interact with many other important medications, Kulkarni noted, "so checking with the prescribing clinician about these possibilities will be important for anyone who will be taking the medication."

Indicated for People 12 and Older

"It's hopeful but it's not the answer to everything. My major concern is for people thinking this is the cure-all," Kunjana Mavunda, MD, a pediatric pulmonologist consultant at multiple KIDZ Medical Services locations throughout South Florida, said when asked to comment.

Clearly with Omicron, a lot of adults and children are getting sick, added Mavunda. Because the Pfizer COVID-19 pill is authorized for ages 12 and older, many children are not eligible.

People starting the regimen early enough in the course of COVID-19 disease to have maximum effect is another potential concern. "The earlier it's taken after infection, the better," Mavunda said. Furthermore, she hopes cost will not be an impediment when Paxlovid is made available in low- and middle-income countries.

Ramping Up Manufacturing

"The FDA authorization of the oral drug, Paxlovid, represents a real leap forward in the fight against COVID-19. With the Omicron variant spreading like wildfire, having a new tool to protect against severe disease is critical," Shoshana Ungerleider, MD, an internal medicine physician at Crossover Health Medical Group in San Francisco, told Medscape Medical News.

Prioritizing access to the antiviral medication for people at higher risk for developing severe disease will be key, she said. "At this point, we believe this pill should work against the Omicron variant, but supply is very limited. My sincere hope is that this new treatment will allow more people with COVID-19 to be treated at home, helping ease the burden on hospitals, which will likely only get worse over the coming weeks."

President Joe Biden addressed availability and distribution in a statement: "Recognizing that this pill takes time to make given the complex scientific process, production will ramp up in the months ahead. We will have over 250,000 treatment courses available to us in January and we will be working with states to ensure those are being distributed equitably and fairly and that our hardest-hit communities are reached," he said.

An Accelerated Authorization?

FDA's authorization for Pfizer's antiviral comes about 5 weeks after the company submitted an application to the FDA. In its submission, the company said a study showed the pill reduced by 89% the rate of hospitalization and death for people with mild-to-moderate COVID-19 illness.

In April, Pfizer announced its antiviral pill for COVID-19 could be available by year's end. In September, an official at the National Institutes of Allergy and Infectious Diseases seconded the prediction.

Merck filed its EUA application with the FDA in October. The company included results of its phase 3 study showing the treatment associated with a 50% reduction in COVID-19 hospitalizations.

Interestingly, in September, Merck announced the findings of laboratory studies suggesting that molnupiravir would work against variants of coronavirus because the agent does not target the virus' spike protein. At the time, Delta was the dominant variant in the US.

Faith-Based Purchasing

The US government has already recognized the potential of these oral therapies, at least in terms of pre-orders.

Last month it announced intentions to purchase $1 billion worth of Merck's molnupiravir, adding to the $1.2 billion worth of the pills the US ordered in June. Last month, the government announced it would purchase 10 million courses of the Pfizer pill at an estimated cost of $5.3 billion.

The government pre-orders of the antiviral pills for COVID-19 are separate from the orders for COVID-19 vaccines. Yesterday, the Biden Administration announced it will make 500 million tests for coronavirus infection available to Americans for free in early 2022.


FDA: Coronavirus (COVID-19) Update: FDA Authorizes First Oral Antiviral for Treatment of COVID-19

Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology, and critical care. Follow Damian on Twitter:  @MedReporter.

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