Product Information

Registration Status: Active

SP-VIRAC 400 TABLET 400mg is approved to be sold in Singapore with effective from 1998-05-08. It is marketed by SPECTRUM HEALTH PROMOTION PTE LTD, with the registration number of SIN09930P.

This product contains Acyclovir 400mg in the form of TABLET. It is approved for ORAL use.

This product is manufactured by SUNWARD PHARMACEUTICAL PTE LTD in SINGAPORE.

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.



A guanosine analog antiviral drug that acts as an antimetabolite. Aciclovir is used for the treatment of herpes simplex virus infections, varicella zoster (chickenpox) and herpes zoster (shingles). Aciclovir has also been investigated for the treatment of herpes labialis applied using an iontophoretic device. Currently approved drugs for the treatment of herpes labialis (cold sores) exhibit low levels of efficacy due to the limited ability of the drugs to penetrate the skin to the site where the herpes virus is replicating. Iontophoresis uses electric current to enhance the delivery of drugs through the skin.


For the treatment and management of herpes zoster (shingles), genital herpes, and chickenpox.

Mechanism of Action

Viral (HSV-1, HSV-2 and VZV) thymidine kinase converts aciclovir to the aciclovir monophosphate, which is then converted to the diphosphate by cellular guanylate kinase, and finally to the triphosphate by phosphoglycerate kinase, phosphoenolpyruvate carboxykinase, and pyruvate kinase. Aciclovir triphosphate competitively inhibits viral DNA polymerase and competes with the natural deoxyguanosine triphosphate, for incorporation into viral DNA. Once incorporated, aciclovir triphosphate inhibits DNA synthesis by acting as a chain terminator. One may consider aciclovir to be a prodrug as it is metabolized to more active compounds. Aciclovir is selective and low in cytotoxicity as the cellular thymidine kinase of normal, uninfected cells does not use aciclovir effectively as a substrate.


The oral bioavailability is 10% to 20%, and decreases with increasing dose. Food does not affect the absorption of acyclovir. The following are the pharmacokinetic parameters for 50 mg buccal tablet, Sitavig, in the saliva: AUC 0 - 24 hours = 2900±2400 mcg.h/mL; Cmax = 440±241 mcg/mL; Tmax = 7.95 ± 4.08 hours.
Hepatic, Acyclovir is metabolized to 9-[(carboxymethoxy)methyl]guanine (CMMG) and 8­ hydroxy-acyclovir (8-OH-ACV) by oxidation and hydroxylation. It is suggested in studies that acyclovir is first metabolized to acyclovir aldehyde by alcohol dehydrogenase and then converted to CMMG. The build up of acyclovir aldehyde may be the cause of acyclovir-induced nephrotoxicity in the absence of crystalluria.


Aciclovir may cause nephrotoxicity (crystallization of aciclovir within renal tubules, elevation of serum creatinine, transient), and neurotoxicity (coma, hallucinations, lethargy, seizures, tremors). Nephrotoxicity and neurotoxicity usually resolve after cessation of aciclovir therapy. However, there is no well-defined relationship between aciclovir concentrations in the blood and these adverse effects.

Active Ingredient/Synonyms

Aciclovir | Aciclovirum | Acycloguanosine | Acyclovir |

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