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SARS-CoV-2 RNA polymerase inhibitor

Molnupiravir

Brand names: Lagevrio

Molnupiravir is an oral antiviral prodrug used for the treatment of mild to moderate COVID-19 in adults at increased risk of progression to severe disease.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

Its active metabolite is incorporated into viral RNA by the SARS-CoV-2 RNA-dependent RNA polymerase, introducing copying errors (lethal mutagenesis) that impair viral replication.

Prescribing in practice

  • It is contraindicated in pregnancy because of potential foetal harm, and effective contraception is required for those of childbearing potential during and for a short period after treatment.
  • It should be started as soon as possible after a positive test and within the recommended early window from symptom onset to be effective.
  • It is not authorised for use in those under 18 because of possible effects on bone and cartilage growth.

Monitoring

No routine laboratory monitoring is required, but pregnancy status and contraception should be confirmed before prescribing.

Counselling the patient

  • Do not take this medicine if you are pregnant, and use reliable contraception as advised.
  • Start the course as early as possible after your positive test and complete the full course.

Evidence & guidelines

Authorisation followed the MOVe-OUT trial, and UK use is guided by MHRA conditional marketing authorisation and NICE recommendations.

Reference: UK COVID-19 therapeutic alerts; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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