UK became the first country in the world to approve an antiviral pill designed to treat symptomatic Covid.

The tablet - molnupiravir - is jointly developed by US-based Merck and Ridgeback Biotherapeutics.

Merck announced its application with the US Food and Drug Administration (FDA) for Emergency Use Authorization (EUA) of molnupiravir is under review and recently announced the European Medicines Agency has initiated a rolling review of the company’s Marketing Authorization Application.

Merck is actively working to submit applications to other regulatory agencies around the world.

“The first global authorization of molnupiravir is a major achievement in Merck’s singular legacy of bringing forward breakthrough medicines and vaccines to address the world’s greatest health challenges,” said Robert M. Davis, chief executive officer and president, Merck.

How does the antiviral pill work? How effective is it? FIT explains.

Molnupiravir is designed to introduce errors into the genetic code of the virus that causes COVID-19. It is taken twice a day for five days as a pill rather than injected or given intravenously.

To be most effective, it needs to be given within five days of developing symptoms.

The pill was initially developed to treat flu.

Earlier clinical trials on 775 patients who had recently caught Covid found that:

• only 7.3 percent of those given the drug were hospitalised

• 14.1 percent who were given given a placebo or dummy pill were hospitalised

• There were no deaths in the Molnupiravir group

• Eight patients who were given a placebo in the trial later died of Covid

The results of the trial are yet to be peer-reviewed.

Viral sequencing done so far has shown molnupiravir is effective against all variants of Covid, Merck has said, including the highly infectious Delta variant.

Merck's antiviral COVID-19 pill could be a game changer, experts believe.

Apart from its effectiveness in preventing severe illness and death, the Merck treatment also has the advantage of being extremely convenient and easy to use.

Merck said it was expecting to produce 10 million courses of the treatment by the end of 2021, with at least 20 million set to be manufactured in 2022, Reuters reported.

The UK has agreed to purchase 480,000 courses with the first deliveries expected in November, BBC reported.

Australia, Singapore and South Korea have also made purchase agreements.

US rival Pfizer has started trials of two different antiviral tablets. Meanwhile, Swiss company Roche is working on a similar medication.

(With inputs from BBC.)