Pharmacology: Pharmacodynamics: Mechanism of Action: Aciclovir is an antiviral agent which is highly active in vitro against herpes simplex virus (HSV) types I and II and varicella-zoster virus. Toxicity to mammalian host cells is low.
Aciclovir is phosphorylated after entry into herpes infected cells to the active compound aciclovir triphosphate. The 1st step in this process is dependent on the presence of the viral-coded thymidine kinase. Aciclovir triphosphate acts as an inhibitor of, and substrate for the herpes-specified DNA polymerase, preventing further viral DNA synthesis without affecting normal cellular processes.
Clinical Studies: There is no information on the effect of Zovirax Cream on human female fertility. In a study of 20 male patients with normal sperm count, oral aciclovir administered at doses of up to 1 g/day for up to 6 months has been shown to have no clinically significant effect on sperm count, motility or morphology.
Pharmacokinetics: Pharmacology studies have shown only minimal systemic absorption of aciclovir following repeated topical administration of Zovirax Cream.
Toxicology: Preclinical Safety Data: The results of a wide range of mutagenicity tests in vitro and in vivo indicate that aciclovir does not pose a genetic risk to man.
Aciclovir was not found to be carcinogenic in long-term studies in the rat and the mouse.
Largely reversible adverse effects on spermatogenesis in association with overall toxicity in rats and dogs have been reported only at systemic doses of aciclovir greatly in excess of those employed therapeutically. Two-generation studies in mice did not reveal any effect of orally administered aciclovir on fertility.