<p>Acyclovir exerts its antiviral e&shy;ects on Herpes simplex virus and Varicella zoster virus by interfering with DNA synthesis and inhibiting viral replication. In cells infected with Herpes virus, the antiviral activity of Acyclovir appears to depend principally on the intracellular conversion of the drug to Acyclovir Triphosphate. Acyclovir is converted to Acyclovir Monophosphate principally via virus coded thymidine kinase, the monophosphate is phosphorylated to diphosphate via cellular guanylate kinase and then via other cellular enzymes to the Triphosphate, which is the pharmacologically active form of the drug.</p>