Product Information

Registration Status: Active

VALACICLOVIR PHARMATHEN INTERNATIONAL FILM-COATED TABLET 500MG is approved to be sold in Singapore with effective from 2015-08-24. It is marketed by GOLDPLUS UNIVERSAL PTE LTD, with the registration number of SIN14832P.

This product contains Valacyclovir 500mg in the form of TABLET. It is approved for ORAL use.

This product is manufactured by PHARMATHEN S.A. in GREECE.

It is a Prescription Only Medicine that can only be obtained from a doctor or a dentist, or a pharmacist with a prescription from a Singapore-registered doctor or dentist.



Valaciclovir (INN) or valacyclovir (USAN) is an antiviral drug used in the management of herpes simplex and herpes zoster (shingles). It is a prodrug, being converted in vivo to aciclovir. It is marketed by GlaxoSmithKline under the trade name Valtrex or Zelitrex.


For the treatment or suppression of cold sores (herpes labialis), herpes zoster (shingles), genital herpes in immunocompetent individuals, and recurrent genital herpes in HIV-infected individuals.

Mechanism of Action

Valaciclovir is phosphorylated by viral thymidine kinase to acyclovir triphosphate (the active metabolite) which then inhibits herpes viral DNA replication by competitive inhibition of viral DNA polymerase, and by incorporation into and termination of the growing viral DNA chain. When used as a substrate for viral DNA polymerase, acyclovir triphosphate competitively inhibits dATP leading to the formation of 'faulty' DNA. This is where acyclovir triphosphate is incorporated into the DNA strand replacing many of the adenosine bases. This results in the prevention of DNA synthesis, as phosphodiester bridges can longer to be built, destabilizing the strand.


After oral administration, valaciclovir hydrochloride is rapidly absorbed from the gastrointestinal tract. The absolute bioavailability of acyclovir after administration of valaciclovir is 54.5% ± 9.1%.
Valaciclovir is rapidly and almost entirely (~99%) converted to the active compound, acyclovir, and L-valine by first-pass intestinal and hepatic metabolism by enzymatic hydrolysis. Neither valaciclovir nor acyclovir is metabolized by cytochrome P450 enzymes.


* Renal cl=255 +/-  86 mL/min [healthy] * apparent cl=86.3 +/- 21.3 mL/min/1.73 m2 [dialysis patients] * apparent cl=679.16 +/- 162.76 mL/min/1.73 m2 [healthy]


Adverse effects of overexposure might include headache and nausea.

Active Ingredient/Synonyms

L-Valine ester with 9-((2-hydroxyethoxy)methyl)guanine | L-Valine, 2-((2-amino-1,6-dihydro-6-oxo-9H-purin-9-yl)methoxy)ethyl ester | Valaciclovirum | Valacyclovir | Valaciclovir |

Source of information: Drugbank (External Link). Last updated on: 3rd July 18. *Trade Name used in the content below may not be the same as the HSA-registered product.


  1. Health Science Authority of Singapore - Reclassified POM
  2. Drugbank