Valaciclovir HCl

CAS 124832-27-5

About the API

Systematic name 2-((2-amino-1,6-dihydro-6-oxo-9H-purin-9-yl)methoxy)ethyl ester monohydrochloride
Trade name(s) Valtrex
Technology Synthetic Organic Chemistry
Molecular Formula C13H20N6O4 HCl
Molecular Weight 360.80 g/mol
Physical properties White to off- white powder
Therapeutic category Antiviral
Available formulations Oral Solid
Regulations EU DMF Flag EU DMF Japan DMF Flag Japan DMF Other Flag Other US DMF Flag US DMF

General Information

Valaciclovir HCl is a drug used to treat viral infections that cause herpes simplex genitalis (genital herpes), herpes labialis (cold sores), and herpes zoster (shingles).

It is a ‘prodrug’, which means it is administered as an inactive precursor and must be metabolized by the body to the active form of the drug. Conversion of inactive valaciclovir to active aciclovir occurs by first-pass intestinal and hepatic metabolism.

Resistance to this drug is rare; however, mutations in viral thymidine kinase and/or viral DNA polymerase have been shown most often to be the cause.


Valaciclovir HCl was first approved by the FDA in 1995 and became available in generic form in 2009.

It is manufactured through large-scale semi-synthetic organic chemistry methods starting with the abundant, commercially available amino acid, L-valine. Semi-synthesis is a type of chemical synthesis that uses compounds isolated from natural sources as starting material.