What Is Methoxsalen ? – Uses, Dosage, Side Effects

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.

Methoxsalen, when activated by long-wavelength UV light in the range of 320-400 nm, is strongly entheogenic, melanogenic, and cytotoxic in the epidermis; the maximal entheogenic activity occurs in the range of 330-360 nm. The mechanisms of action of methoxsalen in inducing repigmentation of vitiliginous skin have not been established. Repigmentation depends on the presence of functioning melanocytes and UV light. Methoxsalen may activate the few functional and dihydroxyphenylalanine-positive melanocytes present in vitiliginous skin. An increase in the activity of tyrosinase, the enzyme that catalyzes the conversion of tyrosine to dihydroxyphenylalanine (a precursor of melanin), has been shown in melanin-producing cells exposed in vitro to trioxsalen and UVA light. In addition, binding of photoactivated psoralens (in triplet states) to pyrimidine bases of nucleic acids, with subsequent inhibitions of DNA synthesis, cell division, and epidermal turnover, has been demonstrated. Following photoactivation, methoxsalen forms covalent bonds with DNA to produce monofunctional (addition to a single strand of DNA) and bifunctional adducts (crosslinking to both strands of DNA). Reactions with other proteins also occur. Psoralens may also increase melanin formation by producing an inflammatory reaction in the skin. Other mechanisms of increased pigmentation may include an increase in the number of functional melanocytes (and possibly activation of dormant melanocytes); enhancement of melanin granule synthesis; stimulation of the movement of melanocytes up hair follicles resulting in melanocytic repopulation of the epidermis; and/or hypertrophy of melanocytes and increased arborization of their dendrites.