HSA Reclassified Drug | Exemptions For Supply of Topical Acyclovir Without Prescription


Eligible Active Ingredient: Topical Acyclovir. As a dermatological preparation not exceeding 5%
With Effective From: 17-Jan-2000
Indication Permitted: Treatment of cold sore
Maximum Daily Dose: Criteria Not Specified
Maximum Supply per Transaction: 2 grams
Minimum Age of User: Criteria Not Specified
Patient Information Leaflet from HSA/PSS: Download PIL (Link to HSA website)

Mechanism of Action of Topical Acyclovir

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.

Additional Information of Topical Acyclovir

Pharmacology Class: Chemotherapeutics For Topical Use
Therapeutic Class: Antibiotics And Chemotherapeutics For Dermatological Use
Chemical Class: Antivirals
Synonyms: Aciclovir | Aciclovirum | Acycloguanosine

Show All HSA-registered therapeutic products granted exemption to supply without prescription


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

HSA-Registered Products Containing Topical Acyclovir As a dermatological preparation not exceeding 5%

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This list is not exhaustive. HSA collaborates with Pharmaceurical Society of Singapore (PSS) to review the appropriate use of therapeutic products in the community from time to time. Hence, HSA may enable the supply of a Prescription Only Medicine (POM) by pharmacists without a prescription, upon review that the product can be used in a safe and effective manner under the supervision of a pharmacist. This can be effected through legislative mechanisms in the absence of an application made by the product registrant to reclassify the therapeutic product, subject to to conditions including indication, strength, maximum daily dose, maximum supply quantity, and age restriction.