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Risk Insights: What to Know About Merck’s New COVID-19 Pill

On 4th November, the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) approved the first antiviral pill, molnupiravir, to be used in response to the coronavirus pandemic. It’s important for both employers and the general public to understand the new pill, how it will be distributed, and any potential side effects.

Clinical Study Findings

Molnupiravir, which will go by the brand name Lagevrio in the UK, was developed by Ridgeback Biotherapeutics and Merck Sharp & Dohme. An international clinical trial found that treatment with the pill decreased the risk of hospitalisation from COVID-19 by approximately 50 per cent. With 775 patients who had recently caught COVID-19, the trial findings were as follows:

  • 7.3% of those given the drug were hospitalised, compared to 14.1% of patients given a placebo.
  • There were no deaths in the group given molnupiravir, but eight patients given a placebo later died of COVID-19.

Molnupiravir is a nucleoside analogue, which means it mimics some of the building blocks of ribonucleic acid (RNA). When coronavirus enters a cell, the virus needs to duplicate its RNA genome to form new viruses. Molnupiravir gets incorporated into burgeoning RNA strands and, once inside, works by introducing errors into the genetic code. This stops the virus from multiplying, reducing the severity of the disease.

Who Will the Pill Be For?

The elderly and those with underlying health conditions have typically experienced worse disease outcomes if exposed to COVID-19. Older people or those with existing ailments often find it harder to produce an effective immune response to infection. Lagevrio will initially be given to the people who need it the most, including those that fall into one of the following categories:

  • Old age
  • Obesity
  • Diabetes
  • Heart disease
  • Cancer

The UK has ordered 480,000 doses of Lagevrio to be received during November. Working alongside the NHS, the government plans to administer the treatment through a national study that examines the long-term safety and effectiveness of the medicine. Both vaccinated and unvaccinated patients who fall into one of the above categories will be given the pill. Further details confirming the study particulars are to be confirmed.


Lagevrio is the first treatment offered at home. It works best when used in mild to moderate COVID-19 cases, so its clear benefit is its ability to target infections early. Intervening in the early stages of the disease could prevent patients from requiring additional treatment and hospitals from becoming overwhelmed. 

Other COVID-19 treatments currently in use include remdesivir and dexamethasone. Both have to be given intravenously or by injection, typically in a hospital setting. Lagevrio, in contrast, is a simple oral pill that can be taken at home.

Dosage Considerations

To be most effective, the MHRA recommends that Lagevrio be used as soon as possible following a positive COVID-19 test and within five days of symptom onset.

The following must be considered:

  • Dosage Recommendation —The recommended dose of Lagevrio is 800 milligrams (mg) (four 200 mg capsules) taken orally every 12 hours for five days.
  • Medicine Administration —Capsules can be taken with or without food and must be swallowed whole with a large glass of water. The capsules mustn’t be opened, crushed or chewed.
  • Missed Doses —If a dose is missed, it can be taken immediately, as long as it was missed less than 10 hours ago. Missed doses over 10 hours must be skipped and the next dose taken as normal. Patients mustn’t double the dose to make up for a missed one.


As Lagevrio works by incorporating itself into RNA strands, concerns have been raised about whether it can incorporate itself into a person’s deoxyribonucleic acid (DNA) and any future associated risks.

However, the pill has been introduced following the government’s independent expert scientific advisory body—the Commission on Human Medicines—conducting a rigorous review of its safety, quality and effectiveness.

Like other medicines, side effects are possible when taking Lagevrio. Common side effects include:

  • Diarrhoea
  • Nausea
  • A dizzy feeling

Less common side effects include vomiting, a rash and hives.

Lagevrio is not recommended for pregnant women. There isn’t sufficient research to know whether it can affect an unborn child. As the treatment could be passed to a baby through breastmilk, women are advised to avoid breastfeeding during treatment and for four days after they’ve finished the last dose.

The introduction of Lagevrio doesn’t change the importance of the vaccine. Being fully vaccinated against COVID-19 is still the best way to mitigate risk.

Risk Mitigation

All medicine carries risks, but there are steps that can be taken to lessen these:

  • Safety instructions should be read before taking Lagevrio, and dosage information must be closely followed.
  • Patients experiencing any unexpected side effects should contact a health professional immediately.
  • Pills should be stored safely away from children.

The introduction of Lagevrio doesn’t change the importance of the vaccine. Being fully vaccinated against COVID-19 is still the best way to mitigate the risk of serious illness and lessen the spread of the disease.


Molnupiravir (Lagevrio) bolsters the UK’s armoury against the virus and may pave the way for similar treatments to be discovered for future pandemics.

For more information on this guidance, contact us today.

Contains public sector information published by GOV.UK and licensed under the Open Government Licence v3.0. The content of this publication is of general interest and is not intended to apply to specific circumstances or jurisdiction. It does not purport to be a comprehensive analysis of all matters relevant to its subject matter. The content should not, therefore, be regarded as constituting legal advice and not be relied upon as such. In relation to any particular problem which they may have, readers are advised to seek specific advice from their own legal counsel. Further, the law may have changed since first publication and the reader is cautioned accordingly. © 2021 Zywave, Inc. All rights reserved.

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