Diphenoxylate Therapy for Psoriasis

To the Editor.—  Regional differences in responsiveness to treatment of psoriatic lesions are commonly observed. Plaques on the knees and elbows are reputed to be more resistant than those on the trunk.¹ We believe that diphenoxylate hydrochloride may be useful in the treatment of these recalcitrant lesions. This hypothesis is based on our observation of a 67-year-old woman with chronic psoriasis who, having been treated for acute diarrhea, experienced a four-month remission of her psoriasis. A combination product of diphenoxylate hydrochloride and atropine sulfate (Lomotil) was prescribed for her treatment.To test this hypothesis we did a double-blind study, which compared topical preparations of diphenoxylate and its placebo. Two patients with chronic psoriatic lesions on their knees applied these preparations twice daily to separate symmetrical lesions. Both showed greater improvement on the diphenoxylate-treated knee.Subsequently, eight patients who had had lesions of psoriasis on their elbows and knees for