Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1       Pharmacodynamic properties

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 first step in this process is dependent on the presence of the HSV-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.

In two large, double blind, randomised clinical studies involving 1,385 subjects treated over 4 days for recurrent herpes labialis, Zovirax Cream 5% was compared to vehicle cream. In these studies, time from start of treatment to healing was 4.6 days using Zovirax Cream and 5.0 days using vehicle cream (p<0.001). Duration of pain was 3.0 days after start of treatment in the Zovirax Cream group and 3.4 days in the vehicle group (p=0.002). Overall, approximately 60% of patients started treatment at an early lesion stage (prodrome or erythema) and 40% at a late stage (papule or blister). The results were similar in both groups of patients.

Pharmacokinetic Properties

5.2       Pharmacokinetic properties
Pharmacology studies have shown only minimal systemic absorption of aciclovir following repeated topical administration of Zovirax Genital.