The FDA said it authorised Paxlovid for emergency use for the treatment of mild-to-moderate disease in adults and children 12 years and older who are at high risk for progression to severe Covid-19.
The drug 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, the FDA said. The pills are meant to be taken every 12 hours for five days.
While the clinical trials did not include patients under the age of 18, Pfizer said, the authorised adult dosing regimen is expected to result in comparable blood concentration levels of the drug in paediatric patients 12 and older weighing at least 40kg.
The second drug, ritonavir, is known to have interactions with some other prescription medicines. Pfizer has said that should be manageable and suggested most patients would be able to lower the dose of their other medications while being treated for Covid-19.
Pfizer said it plans to file a new drug application with the FDA in 2022 seeking full regulatory approval.
Pfizer has agreed to allow generic manufacturers to supply versions of the treatment to 95 low- and middle-income countries through a licensing agreement with international public health group Medicines Patent Pool (MPP).
A rival pill from Merck & Co is under review by the FDA. The drug, molnupiravir, developed with Ridgeback Biotherapeutics, cut hospitalisation and death risk by 30% in a trial.
Pfizer shares ended up more than 1% at $59.45 on Wednesday