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[×] Entry inhibitors
 BRAND NAMES
- International: Zovirax
- Italy: Zovirax
 MECHANISM OF ACTION
Acyclovir is an acyclic guanine nucleoside analogue.
Acyclovir is phosphorylated by viral thymidine kinase to acyclovir monophosphate, the aciclovir affinity to viral thymidine kinase is much greater than for human thymidine kinase and therefore the phosphorylation reaction occurs more rapidly in cells infected with herpes virus than in normal cells.
Subsequently Acyclovir monophosphate is further converted to diphosphate and triphosphate by cellular enzymes.
Acyclovir-triphosphate enters in competition with deoxyguanosine triphosphate, and it's incorporation into viral DNA prevents DNA chain elongation due to the lack of 3'-hydroxyl group. The terminated DNA template containing acyclovir binds the enzyme and leads to irreversible inactivation of the DNA polymerase.
Herpesviruses encoding the thymidine kinase (herpes simplex and varicella-zoster) are much more sensitive to Acyclovir than those that do not encode it (CMV and Epstein-Barr virus).
- Treatment of cold sores caused by Herpes simplex virus
- Treatment of genital herpes lesions
- Cold sores: apply 5 times daily for 4 days.
- Genital lesions: apply every 3 hours up to 6 times daily for 7 days.