Therapy
Randomized, double-blind comparison of 1 mg/L versus 5 mg/L methoxsalen bath-PUVA therapy for chronic plaque-type psoriasis

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Background

Bath–psoralen plus ultraviolet A (PUVA) radiation therapy is increasingly replacing oral PUVA because of its superior short- and long-term safety profile. Several investigations in recent years have led to a refinement of the bath-PUVA protocol; however, the optimal therapeutic concentration of methoxsalen in the bath water has as yet not been delineated.

Objectives

The therapeutic efficacy and tolerability of bath-PUVA by using two different dilutions of methoxsalen (1 mg/L vs 5 mg/L or 0.0001% vs 0.0005%) were compared in 46 patients with chronic plaque-type psoriasis in a prospective, randomized, double-blind study.

Methods

Scores of the Psoriasis Area and Severity Index excluding psoriasis of the head (PASITUL) and the Plaque Severity Index (PSI) were assessed at baseline and at biweekly intervals thereafter until (near)complete clearance or maximal improvement. In addition, methoxsalen plasma levels were determined immediately after the psoralen bath during the first week of treatment and treatment-related side effects were recorded throughout the entire study period.

Results

The median baseline PASITUL score decreased from 11.7 (7.5-32.8) to 3.3 (0.6-1.2) (−72%) in the 1 mg/L methoxsalen group and from 10.8 (6.6-20.7) to 1.4 (03.2) (–87%) in the 5 mg/L methoxsalen group (P < .01). The median baseline PSI score decreased from 9 (6-12) to 3.1 (0.6-10) (–66%) in the 1 mg/L methoxsalen group and from 9.3 (7.3-12) to 1.6 (0-3.6) (−83%) in the 5 mg/L methoxsalen group (P < .01). The median cumulative UVA exposure dose was 25.4 (5.3-81.5) J/cm2 for 5 mg/L methoxsalen and 71.9 (20.7-587.3) J/cm2 for 1 mg/L methoxsalen (P = .001). The number of exposures (22 [11-29] vs 23 [11-34]) and treatment duration (43 [19-68] vs 44 [23-66] days) was comparable for both methoxsalen dilutions (P = .97). Median psoralen plasma levels were 0 (0-26) ng/mL after the 1 mg/L and 30 (0-64) ng/mL after the 5 mg/L methoxsalen immersion (P = .001). Mild to moderate adverse events were more common in the 5 mg/L methoxsalen group.

Limitations

The conclusions of this randomized controlled study are limited by the relatively small sample size.

Conclusions

Our data indicate that in bath-PUVA treatment the use of a high (5 mg/L) methoxsalen concentration is substantially more effective in clearing chronic plaque-type psoriasis than a low (1 mg/L) concentration.

Section snippets

Patients

Forty-six consecutive patients with moderate to severe chronic plaque-type psoriasis were enrolled into the study and randomly allocated to bath-PUVA treatment using a psoralen dilution of 1 or 5 mg/L. Study exclusion criteria included a history of abnormal UVA photosensitivity or cyclosporine administration, severe cardiovascular impairment, or a known allergy to methoxsalen. Before study entry, a wash-out phase of 4 weeks for systemic psoriasis medications and 2 weeks for topical psoriasis

Results

Five of 46 patients did not attend treatment sessions regularly and were excluded from evaluation. Forty-one patients completed the study; of these, 20 had received treatment with 1 mg/L methoxsalen and 21 with 5 mg/L methoxsalen bath-PUVA. The characteristics of the two patient cohorts are given in Table I.

The median MPD for patients photosensitized with 1 mg/L methoxsalen was 2.0 (1-3) J/cm2 as opposed to 0.7 (0.5-1.5) J/cm2 for patients treated with 5 mg/L methoxsalen. Correspondingly, the

Discussion

Various aspects of bath-PUVA treatment using methoxsalen has been investigated in recent years, such as the influence of psoralen bath-water concentration, bath-water temperature, and duration of the psoralen bath on the degree of photosensitization,12, 13, 14, 15 the time course of photosensitization,8, 9, 10 and the therapeutic efficacy of bath-PUVA relative to oral PUVA.4, 5, 6, 7 The impact of methoxsalen concentration on the therapeutic effectiveness of bath-PUVA treatment has as yet,

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Funding sources: None.

Conflicts of interest: None identified.

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Copyright © 2006 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.