Weekly pulse dosing schedule of fluorouracil: a new topical therapy for psoriasis.

We report use of a new weekly pulse dosing schedule of 5% fluorouracil under occlusion for topical treatment of recalcitrant psoriasis. This schedule eliminates the severe local toxicity reported in continuous dosing schedules. The thirteen outpatients completing this study were given continuous topical application of fluorouracil for a mean of 2 to 3 days per week; mean duration of therapy was 15.7 weeks. Eleven patients had an average of 90% clearing of actively treated lesions; 6% clearing was obtained with placebo. At 3-month follow-up examination, improvement was maintained in five patients, was maintained by at least 50% in two, and was lost in four. The five patients with remission at 3 months reported continued remission for up to an additional 8 months. This pulse dosing schedule makes topical fluorouracil under occlusion a useful, safe treatment for limited plaque psoriasis that does not respond to topical corticosteroid therapy.