IT IS A PRODRUG THAT IS METABOLISED TO THE RIBONUCLESIDE ANALOGUE N-HYDROXYCYTIDINE (NHC) WHICH DISTRIBUTES INTO THE CELLS WHERE IT IS PHOSPHORYLATED TO FORM THE PHARMACOLOGICALLY ACTIVE RIBONUCLESIDE TRIPHOSPHATE . RIBONUCLESIDE TRIPHOSPHATE ACTS BY A NECHANISM CALLED AS VIRAL ERROR CATASTROPHE. RIBONUCLESIDE TRIPHOSPHATE INCORPORATION INTO VIRAL RNA BY THE VIRAL RNA POLYMERASE, RESULTS IN AN ACCUMULATION OF ERRORS IN THE VIRAL GENOME LEADING TO INHIBITION OF REPLICATION.