A modified dosage schedule for increased efficiency in PUVA treatment of psoriasis

Ten patients with chronic widespread plaque psoriasis, all of whom had previously completely cleared and suffered a subsequent widespread relapse after conventional PUVA therapy, were treated with a modified UVA dosage schedule, with psoralen formulation and dosage unchanged. Initial and incremental UVA doses were maximized to near-erythemogenic levels as determined by weekly testing for minimal phototoxic dose (MPD), treatment being given three times a week. A comparison of complete psoriasis clearing between the modified treatment and the last PUVA course showed a geometric mean reduction in treatment duration of 55% (P less than 0.001) for a similar number of treatments each week, and a cumulative UVA dose of 31% (P less than 0.05), representing a reduction in treatment duration from 9.1 to 4.1 weeks and cumulative UVA dose reduction of 100.8 to 69.9 J/cm2. Such an improvement in efficiency permits a marked increase in treated patient numbers for the same cost, and is more convenient. The reduction in the total cumulative UVA dose given as larger individual doses also seems likely to lead to a lower incidence of cutaneous long-term, especially carcinogenic, adverse effects.