Topical 8-methoxypsoralen enhances the therapeutic results of targeted narrowband ultraviolet B phototherapy for plaque-type psoriasis

Targeted broadband ultraviolet B (UVB) phototherapy as well as 308‐nm excimer laser have been reported to significantly improve or clear localized psoriatic plaques within 5 to 10 treatments when medium fluences [i.e. 4–6 multiples of minimal erythema doses (MED)] were used. Our study was conducted to determine the effects of different concentrations of topical 8‐methoxypsoralen (8‐MOP) cream when used in combination with targeted UV phototherapy with regard to number of treatments and cumulative UV doses to clear localized psoriasis. Ten evaluable patients with stable plaque‐type psoriasis completed the study. Three different concentrations of 8‐MOP creams (0.001%, 0.01% and 0.1%) were applied prior to irradiation with 4 MEDs of targeted narrowband UVB (NB‐UVB), whereas 0.001% 8‐MOP cream was used in conjunction with 5 J/cm² UVA. All irradiations took place once weekly for 12 weeks. Psoriasis severity index (PSI) score was used to evaluate the efficacy of the treatment. With area‐under‐the‐curve analysis, 0.1% 8‐MOP/NB‐UVB was superior to other modalities in reducing the PSI scores. The number of treatments and cumulative NB‐UVB doses necessary to achieve PSI‐95, a 95% reduction in the scores, was also lower in the 0.1% 8‐MOP/NB‐UVB group, although the differences were not statistically significant. We conclude that topical 8‐MOP cream enhances the therapeutic effects of targeted NB‐UVB phototherapy without significantly increasing the short‐term adverse effects.