Molnupiravir is an antiviral medicine used for the treatment of mild to moderate COVID-19 (caused by SARS-CoV-2) in adults who are at risk of developing severe illness. Molnupiravir may help reduce hospital admission and improve symptoms in COVID-19 patients. It is an emergency use authorized oral therapy for non-hospitalized patients with mild or moderate disease. COVID-19 disease severity classification: 

Asymptomatic or pre-symptomatic infection: Individuals who test positive for SARS-CoV-2 by molecular (PCR) or antigen test but have no symptoms.

Mild illness: Individuals with symptoms such as fever, cough, sore throat, malaise, headache, or muscle pain without shortness of breath, dyspnea, or abnormal chest imaging.

Moderate illness: Individuals with clinical or imaging evidence of lower respiratory tract disease and oxygen saturation (SpO₂) >94% on room air.

Severe illness: Individuals with respiratory rate >30 breaths/min, SpO₂ <94%, PaO₂/FiO₂ <300 mmHg, or lung infiltrates >50%.

Critical illness: Individuals with respiratory failure, septic shock, and/or multiple organ dysfunction.

Molnupiravir is an antiviral agent developed for the treatment of influenza and COVID-19. It is a prodrug of the synthetic nucleoside derivative N4-hydroxycytidine. It exerts antiviral activity by introducing errors during viral RNA replication, including SARS-CoV-2, the causative agent of COVID-19.

Molnupiravir acts as a “tautomer” (shape-shifter), existing in two forms that resemble uracil and cytosine. This leads to transition mutations (U↔C) during viral replication. As a result, the viral RNA accumulates fatal errors, stopping replication, reducing infection duration, and limiting transmission. The viral proofreading enzyme does not effectively remove these errors, allowing lethal mutagenesis to occur.

Molnupiravir inhibits viral replication by inducing widespread mutations in viral RNA through RNA-dependent RNA polymerase. It is converted into the active ribonucleoside analog β-D-N4-hydroxycytidine triphosphate (NHC-TP).

During viral replication, NHC-TP is incorporated into viral RNA instead of cytidine. Due to tautomeric switching, it pairs incorrectly with both guanine and adenine, causing continuous mutation accumulation. This results in viral error catastrophe (lethal mutagenesis), ultimately stopping viral replication.

The recommended dose of Molnupiravir is four 200 mg capsules (4+0+4), every 12 hours for 5 days. Do not give this medicine to children and adolescents aged less than 18 years. The use of Molnupiravir in persons aged less than 18 years has not yet been studied.

No drug interactions have been identified based on the limited available data. No clinical interaction studies have been performed with Molnupiravir. Molnupiravir is hydrolysed to N-hydroxycytidine (NHC) before reaching systemic circulation. Uptake of NHC and conversion to NHC-TP occur via endogenous pyrimidine metabolic pathways. NHC is not a substrate of major drug-metabolizing enzymes or transporters. Based on in vitro studies, neither molnupiravir nor NHC inhibits or induces major drug-metabolizing enzymes or transporters. Therefore, the potential for interaction with concomitant medications is considered unlikely.

Molnupiravir is contraindicated in patients with known hypersensitivity to Molnupiravir.

Common side effects include diarrhoea, nausea, dizziness, and headache.

Animal studies have shown harmful effects on the unborn fetus. Molnupiravir is not recommended during pregnancy. It has not been adequately studied in pregnant women, and its safety is unknown. If you are pregnant, planning pregnancy, or think you may be pregnant, consult your doctor before use. Effective contraception should be used during treatment and for 4 days after the last dose. Breastfeeding is not recommended during treatment and for 4 days after the last dose, as it is not known whether the drug passes into breast milk.

Limited clinical data are available for Molnupiravir. Serious and unexpected adverse reactions may occur that have not been previously reported.

Anti-viral drugs

Store at or below 25°C. Protect from light and moisture. Keep out of reach of children.