Introduction

A naturally occurring furocoumarin compound found in several species of plants, including Psoralea corylifolia. It is a photoactive substance that forms DNA adducts in the presence of ultraviolet A irradiation.

Uses

Methoxsalen is a furocoumarin used to treat psoriasis and vitiligo.

For the treatment of psoriasis and vitiligo

Associated Conditions

Cutaneous T-Cell Lymphoma (CTCL)
Vitiligo
Idiopathic Vitiligo
Refractory peripheral cutaneous T-cell lymphoma
Severe Psoriasis

Pharmacodynamics

Methoxsalen selectively inhibits the synthesis of deoxyribonucleic acid (DNA). The guanine and cytosine content correlates with the degree of Methoxsalen-induced cross-linking. At high concentrations of the drug, cellular RNA and protein synthesis are also suppressed.

Mechanism of Action

After activation it binds preferentially to the guanine and cytosine moieties of DNA, leading to cross-linking of DNA, thus inhibiting DNA synthesis and function.

Route of Elimination

In both mice and man, methoxsalen is rapidly metabolized. Approximately 95% of the drug is excreted as a series of metabolites in the urine within 24 hours (Pathak et al. 1977).

Half Life

Approximately 2 hours

Food Interactions

Take with food. Take this medication with food or milk.

Dosage

Methoxsalen capsules:

Vitiligo therapy: Two Methoxsalen capsules (10 mg each) in one dose taken with milk or food two to four hours before ultraviolet light exposure.

Light exposure: The exposure time to sunlight should comply with the following guide:

Initial exposure: Light-15 min, Medium-20 min, Dark-25 min
Second exposure: Light-20 min, Medium-25 min, Dark-30 min
Third exposure: Light-25 min, Medium-30 min, Dark-35 min
Fourth exposure: Light-30 min, Medium-35 min, Dark-40 min

Subsequent exposure: Gradually increase exposure based on erythema and tenderness of the amelanotic skin. Therapy should be on alternate days and never two consecutive days.

Psoriasis therapy: The Methoxsalen capsules should be taken 2 hours before UVA exposure with some food or milk, according to the following table:

<30 kg body weight: 10 mg
30-50 kg body weight: 20 mg
51-65 kg body weight: 30 mg
66-80 kg body weight: 40 mg
81-90 kg body weight: 50 mg
91-115 kg body weight: 60 mg
>115 kg body weight: 70 mg

Methoxsalen Lotion: is applied to a well-defined area of vitiligo by the physician and the area is then exposed to a suitable credit of UVA. Initial exposure time should be conservative and not exceed that which is predicted to be one-half the minimal erythema dose. Treatment intervals should be regulated by the erythema response; generally once a week is recommended or less often depending on results. The hands and fingers of the person applying the medication should be protected by gloves or finger cots to avoid photosensitization and possible burns.

Pigmentation may begin after a few weeks but significant repigmentation may require 6 to 9 months of treatment. Periodic re-treatment may be necessary to retain all of the new pigment. Idiopathic vitiligo is reversible but not equally reversible in every patient. Treatment must be individualized. Repigmentation will vary in completeness, time of onset, and duration. Repigmentation occurs more rapidly in fleshy areas such as face, abdomen, and buttocks and less rapidly over less fleshy areas such as the dorsum of the hands or feet.

Generic Name	Methoxsalen
Bangla Name	মেথোক্সসালেন
Available brands	2
Language	English বাংলা

Methoxsalen