methoxsalen

Methoxsalen is a photosensitizing drug in the psoralen family, a derivative of furocoumarin used in photochemotherapy. It enhances the skin’s sensitivity to ultraviolet A (UVA) radiation, enabling therapeutic light exposure to treat certain skin disorders.

Medical uses for methoxsalen center on its use with UVA light in PUVA therapy. It is employed to manage conditions such as psoriasis, atopic dermatitis (eczema), vitiligo, and some cutaneous T-cell lymphomas. The drug can be given orally or applied topically in preparations tailored to the condition and treatment plan.

Mechanism and treatment approach: methoxsalen intercalates into DNA and, after UVA exposure, forms covalent bonds with pyrimidine bases, producing cross-links that hinder DNA replication and modulate immune responses in the skin. Following administration, patients become markedly sensitive to light for a period of time, requiring careful protection from incidental sun exposure and dose-guided UVA administration by a clinician.

Safety and adverse effects: Common reactions include nausea, vomiting, dizziness, headache, and phototoxic skin reactions such as redness or itching in sun-exposed areas. Long-term PUVA therapy is associated with an increased risk of skin cancer and photoaging, so cumulative exposure is monitored. Ocular protection is advised during treatment, and methoxsalen is generally contraindicated in pregnancy. It should be used only under medical supervision with appropriate UVA dosing and monitoring for adverse effects.