Methoxsalen G.L. Pharma (Methoxsalen)

Methoxsalen is used in photochemotherapy for disorders of skin pigmentation and proliferation.

• Vitiligo: promotes repigmentation of depigmented skin areas when combined with UVA therapy.
• Psoriasis: reduces plaque formation and scaling through controlled UV‑A exposure.
• PUVA therapy: acts as the photosensitising agent that enables UVA to exert therapeutic effects.

• Methoxsalen intercalates between DNA base pairs and, upon activation by UVA radiation, forms covalent cross‑links with pyrimidine residues. These DNA adducts inhibit DNA synthesis and cell proliferation while also exerting local immunosuppressive effects, thereby modulating abnormal skin cell growth and pigment cell activity.

Methoxsalen may cause a range of adverse reactions, ranging from mild to severe.

Common Side Effects

• Nausea: mild to moderate upset stomach.
• Headache: transient cranial discomfort.
• Erythema: redness of skin at treated sites.
• Pruritus: itching following UVA exposure.
• Phototoxic reactions: heightened skin sensitivity to light.
• Vomiting: occasional emesis after dosing.

Serious or Rare Side Effects

• Severe phototoxic burns: extensive skin injury after UVA.
• Hepatic dysfunction: abnormal liver enzyme elevations.
• Hemolytic anemia: destruction of red blood cells, especially in G6PD deficiency.
• Bone marrow suppression: reduced blood cell production.
• Cardiac arrhythmias: irregular heart rhythms in susceptible individuals.
• Severe nausea/vomiting: persistent gastrointestinal distress requiring medical attention.

Methoxsalen requires careful patient assessment and monitoring before and during therapy.

• Pregnancy: avoid use unless benefits clearly outweigh potential risks.
• Breastfeeding: contraindicated due to unknown excretion in milk.
• Contraindications: do not use in patients with porphyria or systemic lupus erythematosus.
• UV exposure: limit uncontrolled sunlight to prevent unexpected phototoxicity.
• Liver function: monitor hepatic enzymes regularly during treatment.
• Store at below 25°C: keep in original packaging, protect from moisture and direct light.

Methoxsalen can interact with other medications, altering its safety profile.

Major Interactions (Avoid)

• Azathioprine: increased risk of bone marrow suppression.
• Oral retinoids (e.g., acitretin): heightened phototoxicity.
• Other photosensitising agents: additive skin sensitivity.

Moderate Interactions (Monitor Closely)

• Antifungal agents (e.g., itraconazole): may affect methoxsalen metabolism.
• Hormonal contraceptives: potential reduction in contraceptive efficacy.