Metoksalen Maco Pharma (Methoxsalen)

Methoxsalen is used as a photosensitizing agent in dermatologic conditions that respond to UVA‑based therapy.

• Psoriasis: reduces plaque formation and scaling when combined with controlled UVA exposure.
• Vitiligo: promotes repigmentation of depigmented skin areas during PUVA treatment.

• Methoxsalen intercalates between DNA base pairs and, after activation by UVA radiation, forms covalent cross‑links that inhibit DNA synthesis and keratinocyte proliferation. This photochemical action suppresses abnormal skin cell growth, facilitating clinical improvement in psoriatic plaques and enhancing melanocyte activity in vitiligo lesions.

Methoxsalen may cause a range of adverse reactions, most of which are related to its photosensitizing properties.

Common Side Effects

• Nausea: mild to moderate stomach upset after administration.
• Headache: transient cranial discomfort.
• Erythema: redness of skin in treated areas.
• Pruritus: itching that may accompany erythema.
• Hyperpigmentation: darkening of skin where UVA exposure occurs.
• Phototoxic reaction: exaggerated skin response to light.

Serious or Rare Side Effects

• Severe phototoxic burns: extensive skin injury after UVA exposure.
• Hepatic dysfunction: abnormal liver enzyme elevations.
• Anaphylaxis: rare systemic allergic reaction.
• Hemolysis: breakdown of red blood cells, especially in G6PD‑deficient individuals.
• Stevens‑Johnson syndrome: severe mucocutaneous eruption.
• Bone marrow suppression: rare decrease in blood cell production.

Before initiating therapy with Methoxsalen, several safety considerations should be observed.

• Liver function assessment: obtain baseline hepatic enzymes and monitor periodically.
• Skin type evaluation: avoid use in patients with severe photosensitivity disorders.
• Sun exposure avoidance: instruct patients to limit natural sunlight after dosing.
• Concomitant photosensitizers: review all medications that may increase phototoxic risk.
• Pregnancy and lactation: use only if clearly indicated after risk‑benefit analysis.
• Store at room temperature: keep in original container, protect from moisture and direct light.

Methoxsalen can alter the activity of several other medicines, requiring careful management.

Major Interactions (Avoid)

• Warfarin: increased anticoagulant effect, risk of bleeding.
• Tetracyclines: enhanced phototoxicity, leading to severe skin reactions.
• Thiazide diuretics: additive photosensitivity.
• Oral retinoids (e.g., isotretinoin): heightened risk of severe cutaneous reactions.
• Phenobarbital: reduced efficacy of Methoxsalen due to enzyme induction.

Moderate Interactions (Monitor Closely)

• NSAIDs: may modestly increase phototoxic potential.
• Oral contraceptives: possible alteration of hormone levels.
• Antihistamines: may mask early signs of phototoxicity.
• Antifungal agents (e.g., fluconazole): potential for increased plasma levels.
• Vitamin D analogues: monitor for additive skin effects.