The U.S. Food and Drug Administration has authorized the second antiviral pill to treat COVID-19 at home.

The medicine, called molnupiravir and made by Merck and Ridgeback Biotherapeutics, is taken twice a day for five days. Merck says it will have 10 million packs available by the end of the month.

These new antiviral pills could totally change how people treat COVID-19 infections at home, since the only FDA-authorized treatment for nonhospitalized COVID-19 patients is monoclonal antibodies, which typically require an intravenous infusion.

The agency authorized Pfizer’s Paxlovid treatment for COVID-19 on Wednesday.

“Today’s authorization provides an additional treatment option against the COVID-19 virus in the form of a pill that can be taken orally,” Dr. Patrizia Cavazzoni, director of the FDA’s Center for Drug Evaluation and Research, said Thursday.

“Molnupiravir is limited to situations where other FDA-authorized treatments for COVID-19 are inaccessible or are not clinically appropriate and will be a useful treatment option for some patients with COVID-19 at high risk of hospitalization or death,” she added.

The drug works by introducing mutations into the SARS-CoV-2 virus’s genetic code to prevent it from replicating.

FDA didn’t authorize molnupiravir for use in patients younger than 18 because the drug may interfere with bone and cartilage growth.

The agency also said the medicine is not recommended for use during pregnancy because animal studies suggested it could harm the fetus. The FDA warned people who may become pregnant to use a reliable method of birth control while taking molnupiravir until four days after the final dose. Men who are sexually active with women who may become pregnant are advised to use birth control while taking molnupiravir and for at least three months after the final dose.

The pill is available by prescription only, and treatment should begin as soon as possible after a COVID-19 diagnosis and within five days of the onset of symptoms in order to treat mild-to-moderate disease, the FDA said.

Read the full press release here