Home Drug Guide Methoxsalen

Drug Guide

Generic Name

Methoxsalen

Brand Names Oxsoralen, Oxsoralen-ultra, Uvadex

Classification

Therapeutic: Dermatologic agent for vitiligo and psoriasis

Pharmacological: Psoralen derivative (photosensitizer)

FDA Approved Indications

Treatment of vitiligo and psoriasis vulgaris resistant to other therapies

Mechanism of Action

Methoxsalen is a psoralen compound that intercalates into DNA. Upon exposure to UVA light, it forms crosslinks with DNA, inhibiting cell replication and reducing hyperproliferation characteristic of psoriasis and promoting repigmentation in vitiligo.

Dosage and Administration

Adult: Dose varies, typically 0.6 mg/kg orally 2 hours before UVA exposure, 2-3 times weekly; specific protocols depend on condition and response.

Pediatric: Use only if clearly indicated; dosing similar to adults based on body weight, under strict medical supervision.

Geriatric: Dose adjustments may be necessary; closely monitor for adverse effects.

Renal Impairment: No specific adjustments established; use with caution.

Hepatic Impairment: No specific adjustments established; use with caution.

Pharmacokinetics

Absorption: Well absorbed orally, peak plasma levels in 2 hours.

Distribution: Widely distributed, crosses the blood-brain barrier.

Metabolism: Metabolized in the liver via CYP enzymes.

Excretion: Excreted in urine and feces.

Half Life: Approximately 2-10 hours, depending on hepatic function.

Contraindications

Hypersensitivity to methoxsalen or psoralens.
History of photosensitive dermatitis or porphyria.

Precautions

Use with caution in patients with a history of skin cancers or significant liver disease.
Avoid excessive sun exposure outside of UVA therapy sessions.
Patients should avoid pregnancy during therapy due to teratogenic risk.

Adverse Reactions - Common

Nausea (Common)
Headache (Common)
Pruritus or rash after UVA exposure (Common)

Adverse Reactions - Serious

Skin cancer (squamous cell carcinoma, basal cell carcinoma) (Serious, associated with long-term use and UVA therapy)
Photodamage or burns from UVA exposure (Serious)
Visual disturbances, cataracts (Serious)

Drug-Drug Interactions

Other photosensitizing agents, drugs affecting CYP enzymes.
Photosensitizers used concurrently.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor skin for signs of overexposure or burns, and perform baseline eye examinations.

Diagnoses:

Risk for skin injury related to photosensitivity.
Impaired skin integrity.

Implementation: Administer dose 2 hours before UVA therapy, ensure patient uses protective eye-wieces, and monitor the skin and eyes.

Evaluation: Assess for effectiveness of repigmentation, monitor for adverse effects, and document skin changes.

Patient/Family Teaching

Use prescribed dose exactly as directed.
Avoid sun exposure outside of UVA therapy sessions.
Report any skin changes, eye disturbances, or adverse reactions immediately.
Use protective eyewear during UVA treatments.

Special Considerations

Black Box Warnings:

Increased risk of skin cancer with long-term therapy.

Genetic Factors: No specific genetic risk factors identified.

Lab Test Interference: May affect skin biopsy results or skin cancer screenings.

Overdose Management

Signs/Symptoms: Severe nausea, vomiting, skin burns, blurred vision.

Treatment: Supportive care, decontamination if ingestion occurred, and symptomatic treatment.

Storage and Handling

Storage: Store in a cool, dry place, protected from light.

Stability: Stable under recommended storage conditions for the duration of the product's shelf life.