Methoxsalen
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Trade Name
8-Mop, Oxsoralen-Ultra (oral), Uvadex (injection for photopheresis); also generic methoxsalen
Classification
Psoralen; photosensitizing agent
Dosage/Route
- * Dosage:
- – Oral: 10 mg capsules (soft gelatin).
- – Injection (Uvadex): 20 mcg/mL vials.
- * Route: Oral (PO) for PUVA; intravenous (IV) via photopheresis system
Usual Dosage
- * Oral (Psoriasis): 0.4-0.6 mg/kg (based on weight), taken 1.5-2 hours before UVA exposure, 2-3 times weekly.
- * Injection (CTCL): 0.017 mL per mL of apheresis product (approx. 200 mcg total), given during photopheresis, typically 2 consecutive days every 4 weeks for 6 months.
Mechanism of Action
Methoxsalen binds to DNA upon UVA exposure, forming cross-links that inhibit DNA replication and cell division. This slows abnormal skin cell growth (e.g., in psoriasis) or modulates immune response (e.g., in cutaneous T-cell lymphoma via photopheresis)
Side Effects & Adverse Effects
- * Side Effects: Nausea (10%), pruritus (itching), mild erythema post-UVA.
- * Adverse Effects:
- – Severe photosensitivity (burns, blistering).
- – Cataracts (UVA eye damage).
- – Skin cancer (e.g., squamous cell carcinoma, melanoma with long-term use).
- – Rare: Hepatotoxicity, hypersensitivity reactions.
Nursing Management (Implications & Teachings)
- * Implications:
- – Assess skin/eyes before and during therapy (baseline eye exam, monitor for burns).
- – Verify UVA dosing with radiometer; ensure proper timing post-dose.
- – Monitor for nausea or toxicity signs (e.g., liver function if prolonged use).
- * Teachings:
- – Wear UVA-blocking sunglasses for 24 hours post-treatment.
- – Avoid sunlight/tanning beds for 24-48 hours (even through windows); use SPF 30+ sunscreen, cover skin.
- – Take oral dose with food/milk to reduce nausea.
- – Report severe redness, blisters, or vision changes immediately
Indication for This Patient
- * Psoriasis: Severe, recalcitrant cases unresponsive to other treatments (oral + UVA).
- * Cutaneous T-Cell Lymphoma (CTCL): Palliative treatment of skin manifestations (photopheresis).
- * Vitiligo: Repigmentation (less common).
Time
- * Timing:
- – Oral: Take 1.5-2 hours before UVA (Oxsoralen-Ultra peaks faster than older forms).
- – Photopheresis: Administered during procedure, 2 days in a row every 4 weeks.
- * Onset: Photosensitivity peaks at 1.5-2.1 hours (oral); effect visible days to weeks with repeated treatments.
