Comparison of narrow-band (311 nm) UVB and broad-band UVA after oral or bath-water 8-methoxypsoralen in the treatment of psoriasis

Abstract

There is a disparity between the absorption spectrum of 8-methoxypsoralen and the action spectrum for psoralen-sensitized erythema. In an action spectrum corrected for unsensitized reaction 313 and 365 nm have similar efficacies. We evaluated the relative erythemogenic and antipsoriatic efficacy of narrow-band (311 nm) UVB with and without prior psoralen exposure. We also compared the effects of narrow-band UVB and broad-band UVA after oral and bath-water psoralen exposure. Patients with psoriasis underwent half-side comparison studies. In one group the therapeutic efficacy of 311 nm UVB with and without oral psoralen was assessed. The second group received UVA and 311 nm UVB after oral psoralen. The third group was exposed to both radiation sources after bath-water exposure. The erythemogenic, pigmentogenic, and therapeutic efficacy of 311 nm was increased by oral psoralen. With systemic 8-methoxypsoralen, UVA was comparable to 311 nm UVB. After bath-water exposure, 311 nm was clearly superior to broad-band UVA. The efficacy of narrow-band 311 nm UVB can be enhanced by psoralen. Narrow-band 311 nm UVB is also effective after psoralen bath-water delivery.