Valacyclovir (Valtrex)

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General information

Class/mechanism: Antiviral; prodrug of Acyclovir (Zovirax). Valacyclovir is absorbed by the gastrointestinal tract and undergoes first-pass intestinal and/or hepatic metabolism to become acyclovir and L-valine. Acyclovir is a synthetic purine nucleoside analog which interacts with the viral thymidine kinase (TK) encoded by herpes simplex virus types 1 and 2 (HSV-1 & HSV-2) and the varicella-zoster virus (VZV). Thymidine kinase converts acyclovir to acyclovir monophosphate, which is eventually converted via phosphorylation into acyclovir triphosphate. Acyclovir triphosphate inhibits the replication of viral DNA by prematurely terminating the replicating DNA strand since acyclovir has no 3' end; competitively inhibiting viral DNA polymerase; and inactivating viral DNA polymerase. Acyclovir has greater activity against HSV compared to VZV because of more robust phosphorylation by the HSV viral thymidine kinase.[1][2]
Route: PO
Extravasation: no information

For conciseness and simplicity, currently will focus on treatment regimens and not list information such as: renal/hepatic dose adjustments, metabolism (including CYP450), excretion, monitoring parameters (although this will be considered for checklists), or manufacturer. Instead, for the most current information, please refer to your preferred pharmacopeias such as Micromedex, Lexicomp, UpToDate (courtesy of Lexicomp), or the prescribing information.[1]

Diseases for which it is used

Frequently used for the prevention of reactivation of HSV or VZV during antineoplastic treatment. No known antineoplastic properties.

Patient drug information

Also known as

  • Code name: BW-256U
  • Generic names: acyclovir-valine, valaciclovir, valaciclovir Hcl, ValACV
  • Brand names: Talavir, Valcivir, Valtrex, Virval, Zelitrex