Clozapine and olanzapine are better antioxidants than haloperidol, quetiapine, risperidone and ziprasidone in in vitro models.

Although the etiopathogenic mechanisms of schizophrenia (SCZ) are unknown, evidences suggest that excessive free radical production or oxidative stress may be involved in the pathophysiology of SCZ. Antipsychotics are the drugs used in the treatment of SCZ but it remains controversial the impact that typical vs. atypical antipsychotics has on the oxidative stress status in SCZ patients. In vitro, the antioxidant capacity of six antipsychotics was assessed by their ability to: decrease or scavenge reactive oxygen species in the neutrophil respiratory burst; donate hydrogen and stabilize the free radical 2,2-diphenyl-1-picryl-hydrazyl (DPPH); and scavenge 2,2'-azino-di-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS(+)). This study demonstrated that both clozapine and olanzapine have antioxidant effects, in vitro, by scavenging superoxide anion on the respiratory burst, donating electron in the ABTS(+) assay and stabilizing the radical DPPH. Ziprasidone significantly scavenged ABTS(+) and stabilized the radical DPPH whereas risperidone significantly reduced the respiratory burst. Haloperidol and quetiapine lacked antioxidant effects. The chemical structure-related antioxidant capacity suggests a possible neuroprotective mechanism of these drugs on the top of their antipsychotic mechanism of action.