Molnupiravir, an antiviral drug that can be taken at home, has been approved by the UK medicines regulator on 4 November 2021. It is the first medicine taken orally to be approved for use against COVID-19.


The pill, which has the brand name Lagevrio, was developed by the pharmaceutical companies Ridgeback Biotherapeutics and Merck, Sharp and Dohme (MSD). The UK has ordered 480,000 courses, and the first deliveries are expected to arrive in November.

Health and Social Care Secretary Sajid Javid described the drug as a "game-changer". He said: “This antiviral will be an excellent addition to our armoury against COVID-19, and it remains vital everyone comes forward for their life-saving COVID-19 vaccine – particularly those eligible for a booster – to ensure as many people as possible are protected over the coming months.”

What is molnupiravir?

The antiviral drug molnupiravir was originally developed to treat the flu. Since it is an oral drug, it can be taken at home, whereas other treatments are taken intravenously or injected by a healthcare professional.

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The drug is administered to patients with mild-to-moderate COVID-19 within 5 days of symptoms appearing.

How does molnupiravir work?

Molnupiravir works by disrupting the virus's reproduction.

Once the virus gets inside the body's cells, it replicates its genome, which is made not of DNA but RNA (ribonucleic acid). These replicated genomes are then formed into complete virus particles which burst out of the cell and continue to spread around the body.

However, the molecules of molnupiravir are absorbed by virus-infected cells, where they are converted into a defective version of the building blocks of RNA. So, when the virus tries to replicate, the resulting virus particles have defective genetic material and can no longer reproduce. This means that the viral load should remain low, which reduces the risk of serious disease.

Since molnupiravir targets the RNA that SARS-CoV-2 uses as its building blocks, it should be equally effective against all coronavirus variants.

"This mechanism of action has some limitations and the drug cannot be given to pregnant women due to the risk of damaging an unborn baby," said Prof Penny Ward, Visiting Professor in Pharmaceutical Medicine at King’s College London.

How effective is molnupiravir?

“In clinical trials, Lagevrio was found to be effective in reducing the risk of hospitalisation or death for at-risk non-hospitalised adults with mild-to-moderate COVID-19 by 50 per cent," said Professor Sir Munir Pirmohamed, Chair of the Commission on Human Medicines.

In a study that has not been peer-reviewed, 775 patients who had recently caught COVID-19 were given either molnupiravir or a placebo. In the molnupiravir group, 7.3 per cent were hospitalised, and no patients died; 14.1 per cent of the placebo group were hospitalised and there were eight deaths.

“Following a rigorous review of the data by our expert scientists and clinicians, we are satisfied that Lagevrio (molnupiravir) is safe and effective for those at risk of developing severe COVID-19 disease and have granted its approval," said Dr June Raine, Chief Executive of the UK's Medicines and Healthcare products Regulatory Agency (MHRA).

However, the pill must be given within five days after symptoms appear; it is ineffective if it's taken after the patient is hospitalised.

Who will be prescribed molnupiravir?

The MHRA has approved the use of molnupiravir for patients with mild-to-moderate COVID-19 and at least one risk factor, such as obesity, old age, diabetes or heart disease.

The drug may be offered to care homes, and prescribed to vulnerable patients by GPs.

The treatment will be given to both vaccinated and unvaccinated patients in the UK at first as part of a national study to gather more data about its effectiveness.

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.