Comprehensive Monograph: Methoxsalen (DB00553)

Executive Summary

Methoxsalen is a potent, naturally occurring photoactive substance belonging to the furanocoumarin class of compounds.[1] Its therapeutic utility is derived from its function as a photosensitizer, which, upon activation by long-wavelength ultraviolet A (UVA) radiation, becomes pharmacologically active. The fundamental mechanism of action involves the formation of covalent bonds and interstrand cross-links with deoxyribonucleic acid (DNA), leading to the inhibition of DNA replication and cell proliferation.[3] This antiproliferative effect forms the basis of its clinical applications.

The primary therapeutic roles for Methoxsalen are in the management of severe, recalcitrant dermatological and oncological conditions. It is indicated for the symptomatic control of severe, disabling psoriasis; the repigmentation of idiopathic vitiligo; and the palliative treatment of the skin manifestations of cutaneous T-cell lymphoma (CTCL).[1] Treatment is delivered through two distinct modalities: systemic oral administration followed by whole-body UVA irradiation, a procedure known as PUVA (Psoralen + UVA) therapy, and an extracorporeal photopheresis process where a patient's leukocytes are treated

ex vivo with Methoxsalen and UVA light before being reinfused.[5]