Metoxaleno G. L. Pharma (Methoxsalen)

• Methoxsalen is employed in PUVA photochemotherapy for skin disorders that respond to UVA‑activated psoralen.
• Psoriasis: methoxsalen, when combined with UVA exposure, slows keratinocyte proliferation and reduces inflammatory activity, leading to decreased plaque thickness, scaling, and erythema, thereby improving patient quality of life.
• Vitiligo: the drug intercalates into DNA of melanocytes and, upon UVA activation, stimulates melanin production and migration, which can result in repigmentation of depigmented areas and better cosmetic outcomes.
• Other photodermatoses: in specialist settings, methoxsalen may be applied for refractory skin conditions that respond to PUVA, providing an additional therapeutic option when conventional treatments have failed.

• Methoxsalen is a psoralen that intercalates between DNA base pairs. Upon absorption of UVA light, it forms covalent cross‑links with pyrimidine residues, inhibiting DNA synthesis and inducing apoptosis of hyperproliferative skin cells. This immunosuppressive effect reduces inflammatory pathways and normalizes keratinocyte turnover, forming the basis of PUVA therapy. The cross‑linking also alters transcription of cytokine genes, contributing to the therapeutic response.

Methoxsalen may cause a range of adverse reactions, varying from mild to severe, particularly when combined with UVA exposure.

Common Side Effects

• Nausea: transient feeling of sickness, often mild.
• Headache: dull to moderate intensity, usually resolves.
• Skin erythema: redness at treated sites after UVA exposure.
• Pruritus: itching of the skin during or after treatment.
• Hyperpigmentation: darkening of skin in exposed areas.

Serious or Rare Side Effects

• Phototoxic burns: severe skin injury with blistering after excessive UVA.
• Erythema multiforme: target‑like skin lesions requiring medical attention.
• Hepatic dysfunction: abnormal liver enzymes indicating possible liver injury.

Prior to initiating methoxsalen therapy, several precautions should be observed to ensure patient safety and optimal outcomes.

• Dose adjustment: assess renal and hepatic function before treatment.
• Photoprotection: advise patients to avoid excessive sunlight and use protective clothing during therapy.
• Pregnancy: consider use only if potential benefits justify potential risks to the fetus.
• Drug interactions: review concomitant photosensitizing or immunosuppressive medications.
• Store at ambient temperature: keep in original container, protect from light and moisture.

Methoxsalen can interact with other medicines, influencing its efficacy or increasing toxicity.

Major Interactions (Avoid)

• Azathioprine: combined use may heighten bone marrow suppression risk.
• Thiazide diuretics: can amplify photosensitivity reactions.
• Phenobarbital: may reduce methoxsalen activation, decreasing therapeutic effect.

Moderate Interactions (Monitor Closely)

• Acitretin: additive skin irritation may occur.
• Systemic corticosteroids: may modify immune response and affect treatment outcome.