Actinic keratoses were treated with an ointment containing a 1%, 2.5%, or 5% concentration of 5-fluorouracil. The response with the 5% ointment was comparable to our original studies with 20% 5-fluorouracil ointment. The 1% and 2.5% concentrations were found ineffective.
Topical application of 5-fluorouracil labeled with radioactive carbon (14C) in five patients indicated that approximately 6% is absorbed systemically. These data along with repeated hematologic studies suggest that 5-fluorouracil ointment applied to limited skin areas is not absorbed in a degree that would produce general toxicity.
We have concluded that 5% 5-fluorouracil ointment applied twice daily can be used as an effective outpatient treatment in the person with numerous actinic keratoses of the face and neck. Prolonged observation will be required to assess the long term results of this treatment. Actinic keratoses on the hands and arms have not responded completely enough to justify this type of treatment.
One must avoid applications near the lid margins and mucocutaneous junctions. A phototoxic reaction precluded the ointments use when the patient anticipated prolonged sunlight exposure.
DILLAHA CJ, JANSEN GT, HONEYCUTT WM, HOLT GA. Further Studies With Topical 5-Fluorouracil. Arch Dermatol. 1965;92(4):410–417. doi:10.1001/archderm.1965.01600160066015