Simvastatin, som er en inaktiv lakton, hydrolyseres i leveren efter oral indgivelse til den tilsvarende aktive β- hydroxysyre form, som har en potent aktivitet i hæmningen af HMG- CoA reduktase (3 hydroxy – 3 methylglutaryl CoA reduktase).
After oral ingestion, simvastatin, which is an inactive lactone, is hydrolyzed in the liver to the corresponding active beta-hydroxyacid form which has a potent activity in inhibiting HMG-CoA reductase (3 hydroxy – 3 methylglutaryl CoA reductase).