HSA Reclassified Drug | Exemptions For Supply of Atovaquone and Proguanil Without Prescription



Eligible Active Ingredient: Atovaquone/Proguanil HCl. As an oral solid preparation containing Atovaquone and Proguanil HCl 250mg/100mg
With Effective From: 1-Feb-18
Indication Permitted: Malaria prophylaxis. Official guidelines and local information on the prevalence of resistance to antimalarial drugs should be taken into consideration in the selection of chemoprophylaxis of malaria.
Maximum Daily Dose: One 250mg atovaquone/100mg proguanil tablet daily
Maximum Supply per Transaction: Max supply is determined by the duration of travel. Prophylaxis should start 1 to 2 days before entering a malaria-endemic area, and be continued daily until 7 days after leaving the area
Minimum Age of User: Adults 18 years and above, with body weight of at least 40kg.
Patient Information Leaflet from HSA/PSS: Download PIL (Link to HSA website)


Mechanism of Action of Atovaquone/Proguanil HCl

Atovaquone is a hydroxy- 1, 4- naphthoquinone, an analog of ubiquinone, with antipneumocystis activity. The mechanism of action against Pneumocystis carinii has not been fully elucidated. In Plasmodium species, the site of action appears to be the cytochrome bc1 complex (Complex III). Several metabolic enzymes are linked to the mitochondrial electron transport chain via ubiquinone. Inhibition of electron transport by atovaquone will result in indirect inhibition of these enzymes. The ultimate metabolic effects of such blockade may include inhibition of nucleic acid and ATP synthesis. Atovaquone also has been shown to have good in vitro activity against Toxoplasma gondii.
Proguanil inhibits the dihydrofolate reductase of plasmodia and thereby blocks the biosynthesis of purines and pyrimidines, which are essential for DNA synthesis and cell multiplication. This leads to failure of nuclear division at the time of schizont formation in erythrocytes and liver.

Additional Information of Atovaquone/Proguanil HCl

Pharmacology Class: Antimalarials
Therapeutic Class: Antiprotozoals
Chemical Class: Biguanides
Synonyms: 2-(trans-4-(P-Chlorophenyl)cyclohexyl)-3-hydroxy-1,4-naphthoquinone | Acuvel | Wellvone, N-(4-Chlorophenyl)-n’-(isopropyl)-imidodicarbonimidic diamide | 1-(P-Chlorophenyl)-5-isopropylbiguanide | Chlorguanide | Chloroguanide | N-(4-Chlorophenyl)-n’-(isopropyl)-imidodicarbonimidic diamide | Proguanilum


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 Atovaquone/Proguanil HCl As an oral solid preparation containing Atovaquone and Proguanil HCl 250mg/100mg

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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.