The U.S. Food and Drug Administration(FDA) has given emergency authorization to Merck's COVID-19 antiviral pill to treat certain high-risk adult patients. 

The approval of the drug, called monupiravir, comes a day after the FDA granted emergency authorization for Pfizer's antiviral pill, Paxlovid. 

The FDA said on Thursday that the prescription medication is designed to stop the progression of COVID-19 from mild to severe in people at high risk. 

It also noted that the drug by Merck and partner Ridgeback Biotherapeutics could be used when other treatments are not accessible or clinically appropriate. 

The FDA said the drug should only be given to adults because it may affect bone and cartilage growth and is not recommended for use during pregnancy. 

The drug was shown to reduce hospitalizations and deaths by around 30 percent in high-risk individuals, far lower than nearly 90 percent of Pfizer's drug.