Background: Photo-induced eruptions are well-known adverse effects of some neuroleptic drugs, particularly chlorpromazine.
Objective: By a photohemolysis test we assessed in vitro the phototoxic properties of 12 phenothiazines (chlorpromazine, dixyrazine, fluphenazine, levomepromazine, perazine, perphenazine, promazine, promethazine, prothipendyl, thioridazine, trifluoperazine, triflupromazine) and 5 thioxanthenes (chlorprothixene, clopenthixol, flupenthixol, thiothixene, zuclopenthixol).
Methods: Human erythrocytes from 3 donors were incubated with the compounds and irradiated with light sources rich in UVA or UVB, respectively. Doses were up to 100 J/cm2 UVA or up to 1,600 mJ/cm2 UVB. Photo-induced hemolysis was calculated as percentage of complete hemolysis.
Results: Photo-induced hemolysis >10% due to radiation rich in UVA was found with chlorpromazine (maximal median: 98%), dixyrazine (100%), fluphenazine (84%), perazine (100%), perphenazine (100%), promazine (16%), promethazine (25%), prothipendyl (96%), trifluoperazine (100%), triflupromazine (76%), chlorprothixene (100%) and thiothixene (31%). UVB-rich radiation induced hemolysis only with chlorpromazine (73%), dixyrazine (45%) and perazine (60%).
Conclusion: Most neuroleptics are strongly phototoxic in vitro indicating a potential risk for photo-induced reactions also to occur in patients treated with these drugs.