Topical 5-fluorouracil (Efudix)
Author: Blake Mumford


  • Developed in 1957
  • Available in 4% (Tolak) and 5% (Efudix) products
    • Tolak $63, Efudix $55

Mechanism of action

  • 5-FU is converted into active metabolites within the cell:
    • Fluorodeoxyuridine monophosphate, fluorodeoxyuridine triphosphate, and fluorouridine triphosphate


  • Actinic keratoses
  • Squamous cell carcinoma in situ
  • Superficial basal cell carcinoma


  • AK: apply daily or BD until inflammatory response (usually 3 - 4 weeks)
  • SCC in situ: apply BD for at least 6 weeks.
  • Trials have looked at daily vs weekly application; weekly is not as efficacious


  • Do not apply near eyes or mouth
  • Can apply with fingers; wash hands before and after application with soap and water


  • AK
  • SCC in situ: 69% clearance after 4 weeks BD

Side effects

  • Generally well tolerated
  • Pain, pruritus, erythema, irritation, erosion, crusting