Proguanil in malaria prophylaxis

Proguanil as chemoprophylaxis for malaria

Mode of action

• proguanil is converted to an active metabolite cycloguanil which inhibits the enzyme dihydrofolate reductase and interferes with the synthesis of folic acid. It acts as a suppressive and also as a causal prophylactic. Proguanil itself has a second mode of action, mediated by the parent drug rather than its metabolite, which produces synergy with atovaquone (see atovaquone plus proguanil).

Efficacy

• there are very few regions in the world where the local P. falciparum strains are fully sensitive to proguanil.

Prophylactic regimen

• adult dose 200 mg daily, starting 1 week before entering a malarious area, continuing throughout the time in the area and for 4 weeks after leaving the area.

Contraindications

• allergy to proguanil or to any ingredient of the tablets

Cautions

• Renal impairment.
  
  
• Pregnancy (folic acid 5mg daily is required for the length of time that proguanil is taken in pregnancy).

Interactions

• Drugs: May enhance the anticoagulant effect of warfarin
  
  
• Antifolate effect is increased when given with pyrimethamine
  
  
• Vaccines: None reported

Side-effects

Frequently reported are mild gastric intolerance and diarrhoea. Mouth ulcers and stomatitis occur occasionally, particularly when co-administered with chloroquine

Reference

1. UK Health Security Agency. Malaria prevention guidelines for travellers from the UK (online). Last updated April 2025