WHO Model Prescribing Information: Drugs Used in Skin Diseases
(1997; 132 pages) [French] [Spanish] View the PDF document
Table of Contents
View the documentPreface
View the documentIntroduction
Open this folder and view contentsParasitic infections
Open this folder and view contentsInsect and arachnid bites and stings
Open this folder and view contentsSuperficial fungal infections
Open this folder and view contentsSubcutaneous fungal infections
Open this folder and view contentsBacterial infections
Open this folder and view contentsViral infections
Open this folder and view contentsEczematous diseases
Open this folder and view contentsScaling diseases
Open this folder and view contentsPapulosquamous diseases
View the documentCutaneous reactions to drugs
Open this folder and view contentsPigmentary disorders
Open this folder and view contentsPremalignant lesions and malignant tumours
Open this folder and view contentsPhotodermatoses
Open this folder and view contentsBullous dermatoses
View the documentAlopecia areata
View the documentUrticaria
Open this folder and view contentsConditions common in children
View the documentAcne vulgaris
View the documentPruritus
View the documentTropical ulcers
Open this folder and view contentsAntimicrobial drugs
Open this folder and view contentsAntifugal drugs
Open this folder and view contentsAntiseptic agents
Open this folder and view contentsKeratoplastic and keratolytic agents
Open this folder and view contentsScabicides and pediculicides
Open this folder and view contentsAnti-inflammatory and antipruritic drugs1
Open this folder and view contentsAntiallergics and drugs used in anaphylaxis
Open this folder and view contentsUltraviolet radiation-blocking agents (sunscreens)
Close this folderMiscellaneous drugs
View the documentDapsone
View the documentFluorouracil
View the documentMethoxsalen
View the documentPodophyllum resin
Open this folder and view contentsAnnex
View the documentSelected WHO Publications of Related Interest
View the documentBack cover
 

Methoxsalen

Capsule, 10 mg

General information

Methoxsalen (8-methoxypsoralen) is a psoralen derivative that occurs naturally in many plants but is prepared synthetically for therapeutic use. When exposed to ultraviolet A irradiation, it forms photochemical conjugates with nucleic acid that inhibit DNA replication.

It is readily absorbed after oral administration and serum levels peak 2-3 hours after ingestion. The drug is rapidly and extensively metabolized and is excreted in the urine.

Clinical information

Uses

Treatment of severe psoriasis refractory to topical therapy in conjunction with controlled exposure to ultraviolet A radiation (PUVA therapy).

Dosage and administration

Adults and children over 12 years: 0.3-0.4 mg/kg administered 2 hours before exposure to ultraviolet A radiation. Between 12 and 24 sessions are usually necessary. The sessions should be given twice or three times weekly (at least 48 hours apart).

Contraindications

• Hypersensitivity to psoralens.

• Pre-existing diseases associated with photosensitivity including porphyria, acute systemic lupus erythematosus and hydroa vacciniforme.

• Age under 12 years.

• Pregnancy.

Precautions

Treatment should be administered only under the supervision of a physician with special training in photo-chemotherapy.

Protective sunglasses should be worn during therapy and for the following 24 hours in order to avoid the risk of cataract formation.

Patients must be advised to avoid exposure to sunlight for at least 8 hours after therapy.

Adverse effects

Gastric discomfort occasionally occurs.

Cheilitis and transient loss of muscle coordination have been reported. Exposure to ultraviolet radiation after methoxsalen therapy may induce a small degree of pigmentation. PUVA therapy carries an increased risk of cutaneous carcinoma in patients with predisposing factors.

Overdosage

Overdosage of methoxsalen or over-exposure to ultraviolet light following methoxsalen administration can result in severe burning and blistering of the skin. The patient should be placed in a darkened room for at least 24 hours or until the cutaneous reaction has subsided, and supportive measures for the treatment of burns should be initiated.

Induction of emesis or gastric lavage is of value when undertaken within a few hours of ingestion.

Storage

Capsules should be stored in well-closed containers, protected from light.

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