Methoxsalen


Full Prescribing Info
Dosage/Direction for Use

Oral
Repigmentation of vitiliginous areas
Adult: 20 mg or up to 600 mcg/kg 2-4 hr before measured periods of UVA exposure depending on the preparation, given twice wkly or on alternate days, w/ at least 48-hr intervals.

Oral

Psoriasis
Adult: Up to approx 600 mcg/kg, given 1.5-3 hr before UVA exposure, depending on the preparation. Treatment is usually given twice wkly or increased as necessary, w/ at least 48-hr intervals between doses. If there is no or minimal response after the 15th PUVA treatment, dose may be increased by 10 mg and this dose used for the remainder of the treatment course.

Topical/Cutaneous

Psoriasis
Adult: As a 0.15% soln (diluted to 0.015%, if necessary): Apply to affected areas 15 min before UVA exposure. Alternatively, patient may take a whole body bath in methoxsalen soln for 15 min followed by immediate UVA exposure. For treating affected areas, immerse the affected areas for 15 min into 3 mg/L soln of hand and foot soaks followed by a 30-min delay before UVA exposure. Baths or soaks are given twice wkly.

Topical/Cutaneous

Repigmentation of vitiliginous areas
Adult: As 1% soln (diluted to 0.1-0.01%): Apply over lesions then expose to UVA immediately after application or wait up to 2 hr. Protect the area surrounding the lesion w/ a sunscreen. Wash and protect lesions from light after treatment; protection may be up to ≥48 hr. Treatment is usually repeated once wkly. Substantial repigmentation usually requires 6-9 mth of treatment.
Administration
Should be taken with food.
Contraindications
Aphakia, existing or history of melanoma, invasive squamous cell carcinoma, photosensitivity diseases (e.g. porphyria, acute lupus erythematosus, xeroderma pigmentosum).
Special Precautions
Patient exhibiting multiple basal cell carcinoma or history of basal cell carcinoma, previous arsenic therapy, previous x-ray or grenz ray therapy; cardiac diseases or those unable to tolerate prolonged standing or exposure to heat stress; GI diseases or chronic infection. Hepatic impairment. Pregnancy and lactation. Patient Counselling Keep the treated areas protected from light by use of protective clothing or sunscreen. Monitoring Parameters Conduct CBC w/ differential; liver and renal function, antinuclear antibody tests (at baseline and 6-12 mthly); ophth exam (pre-treatment and yrly); signs/symptoms of skin cancer, burns, photosensitivity.
Adverse Reactions
Oral: Nausea, insomnia, nervousness, depression. Photochemotherapy or PUVA: Mild transient erythema, pruritus; dizziness, headache, oedema, vesiculation, acneform eruption, bulla formation, severe skin pain, altered skin or nail pigmentation, onycholysis, premature skin ageing, severe burns, hypertrichosis.
Potentially Fatal: Increased risk of malignant cutaneous neoplasms.
Overdosage
Symptoms: Severe burning and blistering of skin. Management: Oral: Supportive treatment. Induce emesis w/in 2-3 hr after ingestion. Place the patient in a darkened room for at least 24 hr or until cutaneous reactions subside.
Drug Interactions
May increase plasma concentration of drugs metabolised by CYP2A6 isoenzyme. Additive effect w/ other systemic or topical photosensitising agents (e.g. anthralin, coal tar, nalidixic acid).
Food Interaction
Increased risk of phototoxicity w/ food that contain psoralens (e.g. parsley, parsnip, celery). Increased serum concentrations w/ food.
Action
Methoxsalen increases skin reactivity to long-wavelength UV rays. It bonds covalently to deoxyribonucleic acid (DNA), thus inhibiting DNA synthesis and suppressing cell division and epidermal turnover. This effect is used in photochemotherapy or PUVA [psoralen (P) and high-intensity long-wavelength UVA irradiation].
Onset: 1 hr (depending on oral formulation).
Duration: Approx 8 hr.
Absorption: Well but variably absorbed from the GI tract. Time to peak plasma concentration: Approx 1-4 hr.
Distribution: Taken up by epidermal cells; diffuses into eye lens. Plasma protein binding: 75-91% (mainly to albumin).
Metabolism: Almost completely metabolised.
Excretion: Via urine (approx 95% as metabolites, <0.1% as unchanged drug). Elimination half-life: Approx 0.75-2.4 hr.
Storage
Oral: Store between 15-30°C. Protect from light. Topical/Cutaneous: Store between 15-30°C. Protect from light.
ATC Classification
D05AD02 - methoxsalen ; Belongs to the class of topical psoralens used in the treatment of psoriasis.
D05BA02 - methoxsalen ; Belongs to the class of systemic psoralens used in the treatment of psoriasis.
Disclaimer: This information is independently developed by CIMS based on methoxsalen from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to CIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, CIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 CIMS. All rights reserved. Powered by CIMSAsia.com
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