Description
Valacyclovir hydrochloride, an orally active L-valyl ester of the potent antiviral agent aciclovir, was launched in 1995 in the United Kingdom for the treatment of herpes simplex virus (HSV) infections of the skin and mucous membranes, including initial and recurrent genital herpes. As a prodrug, valaciclovir has an improved pharmacokinetic profile to aciclovir. It is rapidly absorbed after oral administration and extensively converted to aciclovir via first-pass metabolism to achieve plasma levels of aciclovir comparable to those seen with aciclovir via i.v. route. Valacyclovir is then activated selectively in virus-infected cells by viral thymidine kinase to form aciclovir triphosphate in a stepwise fashion. This active species inhibits viral DNA polymerase via irreversible binding to the active site of the enzyme. Once aciclovir is incorporated into the elongating viral DNA, it terminates replication of the viral DNA strand, an antiviral mechanism unique to aciclovir. Valacyclovir is reportedly in clinical trials for the suppression of cytomegalovirus infection and disease in renal transplant patients.
Chemical Properties
White Crystalline Powder
Originator
Glaxo Wellcome (United Kingdom)
Uses
Acyclovir (A192400) impurity. The L-Valine ester prodrug of Acyclovir.
Uses
Valaciclovir hydrochloride is an antiviral drug used in the management of herpes simplex, herpes zoster, and herpes B.
Definition
ChEBI: Valacyclovir hydrochloride is an organic molecular entity.
Brand name
Valtrex (GlaxoSmithKline).
General Description
Valacyclovir (Valtrex) is the hydrochloride salt of the Lvalylester of acyclovir. The compound is a water-solublecrystalline solid, and it is a prodrug intended to increase thebioavailability of acyclovir by increasing lipophilicity.Valacyclovir is hydrolyzed rapidly and almost completely toacyclovir following oral administration.
Valacyclovir has been approved for the treatment of herpeszoster (shingles) in immunocompromised patients. Theside effect profile observed in valacyclovir is comparablewith bioequivalent doses of acyclovir.
Pharmacokinetics
The binding of valacyclovir to human plasma proteins ranges between 13.5 to 17.9%. The plasma elimination half-life of acyclovir is 2.5 to 3.3 hours. The bioavailability of valacyclovir hydrochloride is 54%, compared to approximately 20% for oral acyclovir, and it is as effective as acyclovir in decreasing the duration of pain associated with posttherapeutic neuralgia and episodes of genital lesion healing.
Side effects
The adverse effects are similar to acyclovir, which include nausea, headache, vomiting, constipation, and anorexia.
