This activity is due to intracellular conversion of acyclovir to acyclovir triphosphate by viral thymidine kinase. Acyclovir triphosphate inhibits viral DNA synthesis and replication. Treatment of initial and recurrent Herpes simplex infections of the skin and mucous membranes including initial and recurrent genital Herpes simplex infections.
Acyclovir tablets are contra-indicated in patients known to be hypersensitive to acyclovir.
The safety of acyclovir in pregnancy has not been established. Acyclovir should not be administered to pregnant women or nursing women as acyclovir passes into breast milk. Treatment should continue for 5 days, but in a case of severe initial infection the treatment period may have to be extended. In severely immunocompromised patients e.g. after marrow transplant or in patients with impaired absorption from the gut the dose can be doubled to 400 mg or, alternatively, intravenous dosing could be considered. The first dose should be administered as early as possible after the start of an infection and for recurrent episodes this should preferably be during the prodromal period or when lesions first appear.