Clozapine, risperidone, olanzapine, and conventional antipsychotic drug effects on glucose, lipids, and leptin in schizophrenic patients

Some reports have indicated increased rates of diabetes and increased prevalence of glucose and lipid abnormalities during treatment with second-generation antipsychotics, with most concern raised about clozapine and olanzapine. Most of the findings have come from case reports, retrospective examination of laboratory values, and analysis of health-care claims databases. This study investigated fasting levels of glucose, lipids, and leptin in a non-randomized, cross- sectional study of 210 patients, with schizophrenic or schizoaffective disorder, treated with a single antipsychotic medication - clozapine, risperidone, olanzapine, or a conventional antipsychotic. Glucose tolerance tests (GTT), with a 75-g glucose load, were preformed in a subset of patients. In this sample most mean fasting glucose and lipid levels were within the normal range and were not significantly different across the four drug treatment groups. Patients treated with clozapine and olanzapine had higher triglyceride levels than risperidone patients. In patients receiving a GTT, risperidone-treated patients had higher glucose levels at 1 h than patients treated with olanzapine, and there were more patients on risperidone who met American Diabetes Association glucose metabolic criteria for diagnosis of diabetes. Although there were no significant differences in age or body mass index among the four drug groups, we cannot rule out some potential biasing factors we did not assess which could potentially influence our results. These include unknown physician preference in drug selection based on their beliefs about the weight-inducing or diabetes potential of different antipsychotics, differences in visceral fat, and differences in patients' antipsychotic drug history.