Clinical study of a new preparation of 8-methoxypsoralen in photochemotherapy.
BACKGROUND: Oral 8-methoxypsoralen is the drug of choice in photochemotherapy of several dermatoses, e.g., vitiligo and psoriasis. The aim of this trial is to produce a new preparation of the drug, which is able to overcome the difficulties met with the oral use of the older preparations. METHODS: A new preparation containing ultramicronized methoxypsoralen (8-MOP) in 10 mg capsules was tried in an open trial. The trial included 53 patients (15 psoriasis, 26 vitiligo, and 12 tinea versicolor). Light testing showed that the strongest erythema appeared 30 minutes after ingesting the capsules. Patients were exposed to UVA after that period. Laboratory studies were also performed using high performance liquid chromatography to assay the serum concentrations of the drug on normal individuals. RESULTS: Thirteen of the 15 psoriasis patients (87%) showed an excellent response (a remission) after 30 sittings. Twenty-two of the 26 vitiligo patients (85%) showed an excellent response (acceptable repigmentation) after 70 sittings. The 12 patients with tinea versicolor (100%) showed complete repigmentation after 12 sittings. The laboratory studies showed the optimum time to be between 35 to 55 minutes, verifying the clinical observation. CONCLUSIONS: The therapeutic effective dose was found to be 0.25 mg/kg. This new preparation of 8-MOP proved to be well tolerated by the patients, causing no epigastric discomfort, nausea, or vomiting, overcoming the biggest obstacle of oral 8-MOP therapy. It was also well tolerated by patients known to be sensitive to oral and/or topical 8-MOP therapy.