PHOTOSENSITIVITY ASSOCIATED WITH COMBINED UV-B AND CALCIPOTRIENE THERAPY

Background: Ultraviolet B phototherapy is an effective agent for the t reatment of psoriasis; its most frequent: acute side effect is burning of the skin. It has been combined with various other topical or syste mic agents to augment therapeutic effect. Recently, UV-B therapy has b een used with calcipotriene ointment (Dovonex, Westwood-Squibb, Buffal o, NY), a new vitamin D analogue. Observations: We report four cases o f chronic plaque psoriasis that developed in patients who used UV-B ph ototherapy for a substantial period without ill effects and in whom ph otosensitivity reactions within psoriatic plaques developed after calc ipotriene ointment was added, without changes in their UV-B dosage or frequency of treatment. The time from starting calcipotriene therapy t o the development of photosensitivity ranged from 4 to 28 days, and th e number of UV-B exposures during this period varied between one and 1 2 treatments. The mean UV-B dose at burning was 1114 mJ/cm(2). Twenty- two patients had used calcipotriene in combination with UV-B therapy o f a total of 103 UV-B-treated patients during the period when the adve rse events occurred. Half these patients started calcipotriene therapy prior to starting treatment with UV-B. However, cases of photosensiti vity occurred only in the remaining half of the patients in whom calci potriene therapy was added during UV-B therapy. Combined therapy was a ble to be continued or resumed in two patients by reduction of the UV- B dose. In three cases, phototesting confirmed greater photosensitivit y to calcipotriene-treated skin than to skin to which hydrated petrola tum was applied. Conclusions: Calcipotriene ointment should be introdu ced with caution in patients already receiving UV-B phototherapy, part icularly those receiving high doses of UV-B. The mechanism of this pho tosensitivity reaction is unknown. This increased sensitivity to UV-B may be a result of the effect of calcipotriene on stratum corneum thic kness, epidermal melanization, a result of its effect on the inflammat ory reaction to UV-B irradiation, or, possibly, because it is a photot oxic agent.