The relationship between negative symptoms of schizophrenia and extrapyramidal side effects with haloperidol and olanzapine

Atypical neuroleptics present a unique opportunity to examine confounding by neuroleptic-induced extrapyramidal symptoms (EPS) in the assessment of negative signs of schizophrenia. EPS, such as facial bradykinesia and akinesia, involve some of the same response systems and phenomena as emotional display channels. EPS are attributed to the blockade of dopamine receptors in the striatum by traditional neuroleptics. Newer atypical neuroleptics target primarily mesolimbic and mesocortical areas, and receptors for other transmitters such as serotonin. Olanzapine has been reported as less likely to cause EPS and may improve some negative signs. We investigated the relationship between measures of EPS and negative symptoms in patients with schizophrenia treated with haloperidol or olanzapine. Patients were rated with the Positive and Negative Syndrome Scale (PANSS) and the Simpson-Angus Scale EPS scale. Results show that the two agents have comparable efficacy but different safety outcomes. A positive correlation between EPS end PANSS negative score was detected in the haloperidol group only. Stepwise multiple regression analysis shows that a big proportion of variability in PANSS negative symptoms is predicted by EPS in the haloperidol group, but not in the olanzapine group, even though EPS increased in patients treated with haloperidol but not in olanzapine patients.