Half-side comparison of erythemogenic versus suberythemogenic UVA doses inoral photochemotherapy of psoriasis

Background: Early American and European multicenter trials on the efficacy of photochemotherapy (PUVA) for psoriasis have clearly shown that the treat ment protocol has a crucial impact on the cumulative LNA dose required for clearing patients, Most, if not ail, treatment protocols rely on the PUVA-i nduced erythema as a guideline for UVh dosimetry! Objective,: Our aim was to investigate whether phototoxic erythema is integ ral to an optimized PUVA protocol or reflects an unnecessary overexposure o f patients. Methods: A standard high-dose WA regimen using minimal phototoxic, doses (h LPD) was compared against two different low-dose regimens. To this purpose a bilateral comparison study was performed on 31 patients and divided in tw o parts. In the first trial on 14 patients, half of each patient's body was irradiated at each visit with 1 MPD, whereas the other half received only two thirds of the MPD. In the second trial on 17 patients treatment with 1 MPD was compared against treatment with one half of the MPD. Results: A total of 27 patients (12 patients in the first trial, 15 patient s in the second trial) completed the study In both trials the suberythemoge nic doses were therapeutically as effective as the minimal phototoxic doses . Conclusions: We conclude that PUVA-induced erythema is not a prerequisite f or effective psoriasis treatment and that a low-dose WA regimen is a promis ing approach to increase the short- and long-term safety of photochemothera py.