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Author: Admin | 2025-04-28
Package insert / product labelDosage form: tabletDrug class: Purine nucleosides Acyclovir Tablets Description Acyclovir is a synthetic nucleoside analogue active against herpesviruses. Acyclovir tablets, USP is a formulation for oral administration. Each Acyclovir Tablet contains 400 mg or 800 mg of acyclovir. In addition, each tablet contains the inactive ingredients colloidal silicon dioxide, magnesium stearate, microcrystalline cellulose, povidone and sodium starch glycolate. The 400 mg and 800 mg tablet also contains ferric oxide and FD&C blue lake # 2 Indigo carmine AL, respectively. Acyclovir USP is a white to off white crystalline powder, slightly hygroscopic with the molecular formula C 8H 11N 5O 3 and a molecular weight of 225.20. The maximum solubility in water at 37°C is 2.5 mg/mL. The pka's of acyclovir are 2.27 and 9.25. The chemical name of acyclovir is 6H-Purin-6-one, 2-amino-1,9-dihydro-9-[(2-hydroxyethoxy)methyl]-. It has the following structural formula: VIROLOGY Mechanism of Antiviral Action: Acyclovir is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against herpes simplex virus types 1 (HSV-1), 2 (HSV-2), and varicella-zoster virus (VZV). The inhibitory activity of acyclovir is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV and VZV. This viral enzyme converts acyclovir into acyclovir monophosphate, a nucleotide analogue. The monophosphate is further converted into diphosphate by cellular guanylate kinase and into triphosphate by a number of cellular enzymes. In vitro, acyclovir triphosphate stops replication of herpes viral DNA. This is accomplished in 3 ways: 1) competitive inhibition of viral DNA polymerase, 2) incorporation into and termination of the growing viral DNA chain, and 3) inactivation of the viral DNA polymerase. The greater antiviral activity of acyclovir against HSV compared with VZV is due to its more efficient phosphorylation by the viral TK. Antiviral Activities: The quantitative relationship between the
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