Information about Methoxsalen
8-methoxsalen and 5-methoxsalen are furocoumarins referred to collectively as psoralens that have photosensitizing activity and are used orally and topically in conjunction with ultraviolet irradiation for the therapy of psoriasis and vitiligo.
Liver safety of Methoxsalen
Psoralens have been linked to a low rate of transient serum enzyme elevations during therapy and to rare instances of clinically apparent acute liver injury.
Mechanism of action of Methoxsalen
Psoralen is a natural furocoumarin found in the seeds of Psoralea corylifolia and other botanicals and used for their photosensitizing activity in the therapy of psoriasis and vitiligo. Psoralen is actively taken up by epidermal cells and intercalates into DNA. Upon exposure to ultraviolet (UV) light, psoralen forms cross links between DNA causing cell injury and death.
FDA approval information for Methoxsalen
The most commonly used form of psoralen, known as 8-methoxsalen or methoxypsoralen, has been available in the United States since the 1950s and was typically administered orally or as an ointment with ultraviolet light treatment. 8-methoxsalen with ultraviolet radiation (PUVA) was approved for use in refractory psoriasis in the United States in 1982. Its current indications are limited to severe, recalcitrant and disabling psoriasis. It also has been used to treat vitiligo and cutaneous T cell lymphoma. Psoralen is now not commonly used, largely because of concerns over the long term safety of ultraviolet light therapy and the availability of newer, more effective and better tolerated agents for psoriasis.
Dosage and administration for Methoxsalen
8-methoxsalen is available in 10 mg capsules for oral use and as lotions of 1% methoxsalen for topical administration generically and under the brand name Oxsoralen. The typical oral dose is adjusted by weight and ranges from 10 to 70 mg, 2 to 4 times weekly taken 1 to 2 hours before a controlled dose of ultraviolet irradiation.
Side effects of Methoxsalen
Common side effects include nausea, headache, dizziness, fatigue, depression and erythematous and pruritic skin reactions to UV light. Rare, but potentially severe adverse reactions include increased risk of basal cell carcinoma and melanoma.
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