Abstract
A possible photochemical process leading to photosensitivity due to mequitazine (MQZ) was studied in comparison with that of chlorpromazine (CPZ). Although MQZ was stable to irradiation with UVA light in ethanol or benzene, it was assumed that MQZ S-oxide was produced in aqueous solution. UVA irradiation of a skin surface lipid squalene in the presence of MQZ produced squalene hydroperoxide. Preferential involvement of Type II reaction (mediation of singlet molecular oxygen) in the photosensitized oxidation with MQZ was likely although Type I reaction (radical mechanism) was also involved in the photosensitized oxidation with CPZ. Since reaction rates of photosensitization in in vivo systems are dependent on microenvironments around photosensitizer molecules and target molecules, in vitro study on solvent dependency of the reaction rates has a critical significance.
