Acyclovir Tablets acyclovir

Subject: Herpes Treatment
Description: Acyclovir has an antiviral effect on herpes simplex viruses and varicella zoster virus
Category: Health

Acyclovir 400mg and 800mg tablets

Presentation

GLOBAL ACYCLOVIR 400mg tablets are white, oval biconvex tablets identified ACY400 on one side. Each tablet contains 400mg acyclovir and typically weighs 525mg.

GLOBAL ACYCLOVIR 800mg tablets are white, oval biconvex tablets identified ACY800 on one side and a breakline on the other. Each tablet contains 800mg acyclovir and typically weighs 1050mg.

Uses

Actions

Acyclovir is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against human herpes viruses, varicella-zoster virus, Epstein-Barr virus and to a lesser extent cytomegalovirus.

Acyclovir has an antiviral effect on herpes simplex viruses and varicella zoster virus resulting from its interference with DNA synthesis leading to inhibition of virus replication. The exact mechanism of acyclovir action in other susceptible viruses has not been fully elucidated.

Acyclovir triphosphate is the pharmacologically active metabolite of the drug. The initial phosphorylation of acyclovir to acyclovir monophosphate is catalysed by virus-induced thymidine kinase. Thus selective activation of the drug is achieved principally in infected cells. Further phosphorylation to acyclovir diphosphate is catalysed via cellular guanylate kinase and then phosphorylation to acyclovir triphosphate is catalysed via other intracellular enzymes (phosphoglycerate kinase, pyruvate kinase, phosphoenolpyruvate carboxykinase) . The extent of formation of acyclovir monophosphate, diphosphate and triphosphate is directly related to the concentration of acyclovir in the cellular culture medium. In vitro studies indicate that acyclovir tri-phosphate is produced in low concentrations via unidentified cellular phosphorylating enzymes in cells infected with Epstein-Barr virus and cytomegalovirus.

Acyclovir triphosphate inhibits DNA synthesis by competing with deoxyguanosine triphosphate for viral DNA polymerase. Viral DNA polymerase exhibits a 10- to 30-fold greater affinity for acyclovir triphosphate than does cellular ?-DNA polymerase. Following incorporation of acyclovir triphosphate into the growing viral DNA chain, DNA synthesis is terminated. Cytomegalovirus does not produce thymidine kinase and so the antiviral activity of acyclovir in cytomegalovirus-induced infections is poor. The selective action of acyclovir on the infected cells is due to poor uptake of acyclovir into uninfected cells, minimal phosphorylation of acyclovir to acyclovir monophosphate in uninfected cells and low cellular DNA polymerase affinity for acyclovir triphosphate.