Methoxsalen

What it is and how it works

Mechanism class: Photoabsorption

Indications

III. INDICATIONS AND USAGE Photochemotherapy (Methoxsalen with long wave UVA radiation) is indicated for the symptomatic control of severe, recalcitrant, disabling psoriasis not adequately responsive to other forms of therapy and when the diagnosis has been supported by biopsy. Methoxsalen is intended to be administered only in conjunction with a schedule of controlled doses of long wave ultraviolet radiation.

Dosage and administration (summary)

IX. DRUG DOSAGE & ADMINISTRATION CAUTION: Methoxsalen Capsules, USP represents a new dose form of methoxsalen. This new dosage form of methoxsalen exhibits significantly greater bioavailability and earlier photosensitization onset time than previous methoxsalen dosage forms. Each patient should be evaluated by determining the minimum phototoxic dose (MPD) and phototoxic peak time after drug administration prior to onset of photochemotherapy with this dosage form. Human bioavailability studies have indicated the following drug dosage and administration directions are to be used as a guideline only. PSORIASIS THERAPY 1.

Contraindications

IV. CONTRAINDICATIONS A. Patients exhibiting idiosyncratic reactions to psoralen compounds. B. Patients possessing a specific history of light sensitive disease states should not initiate methoxsalen therapy except under special circumstances. Diseases associated with photosensitivity include lupus erythematosus, porphyria cutanea tarda, erythropoietic protoporphyria, variegate porphyria, xeroderma pigmentosum, and albinism. C. Patients with melanoma or with a history of melanoma. D.

Warnings and precautions

V. WARNINGS - GENERAL A. SKIN BURNING: Serious burns from either UVA or sunlight (even through window glass) can result if the recommended dosage of the drug and/or exposure schedules are exceeded. B. CARCINOGENICITY: ANIMAL STUDIES: Topical or intraperitoneal methoxsalen has been reported to be a potent photocarcinogen in albino mice and hairless mice (Hakim et al., 1960 10 ). However, methoxsalen given by the oral route to Swiss albino mice suggests this agent exerts a protective effect against ultraviolet carcinogenesis.

Pregnancy

F. PREGNANCY: Animal reproduction studies have not been conducted with methoxsalen. It is also not known whether methoxsalen can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Methoxsalen should be given to a woman with reproductive capacity only if clearly needed.

Storage and supply

XII. HOW SUPPLIED Methoxsalen Capsules, USP 10 mg is green color, oval shaped soft gelatin capsule imprinted with 'M10' containing no drug crystals and clear colorless to pale yellow liquid, each containing 10 mg of methoxsalen (8-methoxypsoralen). It is packed in amber colored glass bottles as 50's count (NDC 64380-752-16).

Source: Methoxsalen (Methoxsalen) — US FDA prescribing information, 2026-06-24, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.