Propylthiouracil in psoriasis: results of an open trial

Propylthiouracil (PTU) is an antithyroid thioureylene that has immune modulatory and free radical scavenging abilities. In view of the immunomodulatory effects of PTU, we decided to study the therapeutic response of patients with psoriasis to oral PTU.

Our purpose was to study the effect of oral PTU in patients with stable plaque psoriasis.

Oral PTU, 100 mg, was administered every 8 hours for 8 weeks to 10 patients with long-standing psoriasis. Skin biopsy specimens were taken from the lesions before and at the end of the study. Clinical response was monitored with the Psoriasis Area and Severity Index scoring system. Histologic scores were graded with a 5-point grading scale. Complete blood cell count was obtained at the beginning and at the end of the study. Thyroid-stimulating hormone (TSH) was obtained at the beginning and every 2 weeks thereafter until completion of the study.

Three patients dropped out of the study. Of the remaining seven, two showed near-complete resolution of their psoriatic lesions, whereas the remainder showed moderate improvement in their clinical scores. Histologic scores were significantly improved in the group with all but one patient showing improvement or no change. Thyroid function tests were unchanged in all but one patient who showed a slight increase in serum TSH at the sixth week of therapy.

Because of its low toxicity relative to other oral treatments of psoriasis, PTU may have a role in the treatment of patients with this disorder.