What drugs are used to stimulate skin pigmentation? How do they work?

The psoralens or furocoumarins, potent photosensitizing drugs, have been used for thousands of years to stimulate skin pigmentation. The most commonly used agent in dermatology for skin photosensitization is 8-methoxypsoralen (8-MOP). The exact mechanism of skin photosensitization is not known, but 8-MOP is preferentially taken up by epidermal cells, where it binds to cell membranes and is concentrated within cell nuclei. Upon photoactivation, 8-MOP causes alteration in cell membrane signaling and forms covalent bonds with DNA that lead to the formation of psoralen- DNA adducts. Together, the altered cell membrane signaling and psoralen-DNA adducts incite a cascade of events that stimulate melanocyte melanin synthesis and melanin transfer to keratinocytes, resulting in increased skin pigmentation.