Molnupiravir antiviral drug, molecular model. Molnupiravir is a medication for Covid-19. The molecule is a prodrug for a derivative of the nucleoside cytidine. The enzyme RNA (ribonucleic acid) polymerase incorporates the analogue into viral RNA in place of cytidine and also uracil. In right locations, these random mutations inhibit reproduction of the virus. Atoms are colour-coded: carbon is black; hydrogen is white; nitrogen is blue; oxygen is red.