By Jim Reed, BBC Health Reporter
The UK Medicines Regulatory Agency (MHRA) approved on Thursday the oral drug designed to treat symptomatic COVID-19.
Molnupiravir can be administered twice daily to patients who have tested positive and who have at least one risk factor for developing severe disease.
Originally developed to treat the flu, it reduced the risk of hospitalizations and deaths by half during clinical trials.
British Health Minister Sajid Javid said the treatment is "revolutionary" for the most vulnerable and immunocompromised.
Molnupiravir was designed by the American pharmaceutical companies Merck, Sharp and Dohme and Ridgeback Biotherapeutics.
It is an oral antiviral medication for COVID-19.
The pill acts on the enzyme that the virus uses to replicate , thus introducing errors into its genetic code.
This action would prevent its multiplication, keeping the viral load low and reducing the severity of the disease.
Merck said this mechanism should make the treatment equally effective against any new variants of the virus that may emerge.
The MHRA announced that the tablet was authorized for use in people with mild to moderate symptoms and with at least one risk factor associated with greater severity of the syndrome, such as obesity, advanced age, diabetes and coronary disease.
The organization's executive director, Dr. June Raine, described it as "another therapy to add to our armor against COVID-19."
"It is the first antiviral in the world approved for this disease that can be taken orally instead of being administered intravenously," he added.
This way, it can be taken at home or outside the hospital, before the disease progresses to a more serious state.
Clinical trials
During clinical trials, molnupiravir was administered to 775 patients who had recently contracted COVID-19, and it was observed that:
- 7.3 % of those who took the pill were hospitalized, compared to 14.1% of those who were given a placebo .
- There were no deaths among those who took molnupiravir, while in the placebo group eight died from the disease.
The data was published in a press release and has not yet been peer-reviewed.
The trial results suggest that molnupiravir must be taken soon after symptoms develop to be effective.
A previous study in patients who had already been hospitalized for severe COVID-19 was stopped because its results had been disappointing.
Merck is the first company to report the results of a trial of a pill to treat Covid-19, but other companies are working on similar treatments.
US-based Pfizer has begun testing two antiviral tablets, while Swiss company Roche is working on a similar drug.