Metoxsalene S.A.L.F. (Methoxsalen)

Methoxsalen is used in dermatologic conditions that respond to PUVA therapy, targeting abnormal skin cell proliferation and depigmentation.

• Psoriasis: reduces scaling, erythema and plaque thickness.
• Vitiligo: promotes repigmentation of depigmented patches.
• Cutaneous T‑cell lymphoma: used as part of PUVA protocols to control skin lesions.

• Methoxsalen intercalates into DNA strands and, upon activation by UVA light during PUVA therapy, forms covalent cross‑links between DNA bases. These cross‑links inhibit DNA synthesis and cell division, leading to reduced proliferation of hyperactive keratinocytes and melanocytes, thereby normalizing skin appearance.

Methoxsalen may cause a range of adverse reactions, from mild to severe, depending on exposure and patient factors.

Common Side Effects

• Nausea: transient gastrointestinal upset after administration.
• Headache: mild to moderate intensity during treatment.
• Erythema: redness of skin at treated sites.
• Itching: pruritus associated with phototoxic reaction.
• Hyperpigmentation: darkening of exposed skin areas.
• Phototoxicity: heightened skin sensitivity to UVA.

Serious or Rare Side Effects

• Severe burns: deep skin injury from excessive UVA exposure.
• Blistering: formation of fluid‑filled lesions on irradiated skin.
• Cutaneous malignancies: increased risk of skin cancer with long‑term use.
• Ocular cataracts: lens opacity from systemic exposure.
• Hemolysis in G6PD deficiency: rapid destruction of red blood cells.
• Systemic hypersensitivity: rare allergic reactions requiring medical attention.

Methoxsalen requires careful patient assessment and monitoring to minimize risks.

• Assess skin type: evaluate for high phototype or history of skin cancer.
• Avoid excessive UVA: limit exposure time and intensity during PUVA sessions.
• Monitor ocular health: schedule regular eye examinations for cataract detection.
• Check G6PD status: contraindicated in patients with glucose‑6‑phosphate dehydrogenase deficiency.
• Store at ambient temperature: keep below 25°C, in original packaging, protected from moisture and light.

Methoxsalen can interact with other agents that influence photosensitivity or coagulation.

Major Interactions (Avoid)

• Azathioprine: additive immunosuppression may increase infection risk.
• Cyclosporine: combined phototoxic effects can exacerbate skin damage.
• Retinoids (e.g., acitretin): heightened photosensitivity and mucocutaneous toxicity.

Moderate Interactions (Monitor Closely)

• Oral contraceptives: possible reduction in efficacy due to hepatic enzyme induction.
• Antifungal azoles (e.g., ketoconazole): may alter methoxsalen metabolism.
• Anticoagulants (e.g., warfarin): monitor INR as phototherapy can affect vitamin K levels.