Psoralens and related compounds in the treatment of psoriasis.

PUVA therapy has radically altered the management of severe psoriasis. It is of greatest benefit in those patients with extensive involvement, and in those unresponsive to conventional therapy. The long term side effects of PUVA currently limit its use to patients with disabling disease. The full extent of long term side effects has yet to be defined. In order to reduce the toxicity and improve the efficacy of PUVA, a better understanding of the molecular aspects of psoralen-DNA interaction, DNA repair, and mutagenesis is required. The action spectrum of PUVA in clearing psoriasis has yet to be defined. By limiting the spectrum of UVA exposure it may be possible to reduce some of the toxic effects of PUVA. The recent advances in the formulation of 8-MOP preparations has yielded a drug with more predictable pharmacokinetics and clinical response. Further research with newer psoralens may produce more effective and less toxic compounds. In the last ten years, PUVA has been both a valuable addition to dermatologists' clinical armamentarium and a useful tool in increasing our understanding of cellular biology and the interaction between ultraviolet radiation and biologic systems.