Effects of olanzapine and clozapine upon pulse rate variability

Based upon their in vitro receptor binding profiles, the atypical antipsychotics clozapine and olanzapine exhibit cholinergic receptor binding of similar potency. Data comparing the in vivo anticholinergic effects, however, of these neuroleptics upon neurocardiac control are sparse. The goal of this study was to compare the in vivo effects of clozapine and olanzapine upon neurocardiac control by assessment of the pulse rate variability (PRV) in schizophrenic patients and healthy controls. Twenty patients with schizophrenia (according to DSM‐III‐R criteria) treated with either clozapine (100–600 mg/day) or olanzapine (10–20 mg/day), and ten healthy controls, were recruited into the study. PRV was assessed by continuously recording the skin blood volume in the fingertip of the second digit under resting conditions and PRV parameters were calculated. When significant differences in PRV parameters between the patients and controls were detected by Kruskal‐Wallis tests, Mann‐Whitney tests were used to test for group differences between the olanzapine‐ and clozapine‐treated patients. In comparison to the healthy controls, the PRV parameters of the clozapine‐ and olanzapine‐treated schizophrenic patients were significantly reduced. Indeed the reduction of PRV was significantly greater in the clozapine‐treated group compared to the olanzapine‐treated group (P