The topic of antipsychotic-induced weight-gain and its relationship to glucose metabolism is under-studied. We evaluated the long-term effects of a new-generation antipsychotic, quetiapine and a conventional antipsychotic, haloperidol on body mass index (BMI) and glycaemic control in patients with schizophrenia previously treated with conventional antipsychotics. Forty-five clinically stable patients with schizophrenia participated in this randomized, investigator-blinded, parallel-group comparison of flexible doses of quetiapine and haloperidol treatment over 52 wk. Primary outcome measures were change from baseline in BMI and glycosylated haemoglobin (HBA1c) levels. There were no between-group differences at any of the time-points for BMI (F=1.90, p=0.1) and HBA1c (F=1.17, p=0.3) values, and there were no significant changes in BMI from baseline for either group. HBA1c levels decreased significantly at end-point for the haloperidol group (−1.5%, p=0.04), but not for the quetiapine group (−0.3%, p=0.5). Although the sample was not generally obese (mean baseline BMI 25.5±6.3 kg/m2), a large proportion exhibited evidence of abnormal glycaemic control prior to randomization (mean HBA1c 6.7±1.9%), with 48% having values that were at least mildly elevated (HBA1c >6.1%) and 19% markedly elevated (HBA1c >7%). The number of subjects with elevated HBA1c values decreased from baseline in both the haloperidol and quetiapine treatment groups. These findings suggest that switching treatment from a conventional antipsychotic to quetiapine is not associated with weight gain or worsening of glycaemic control, even in the long term. The study also highlights the high incidence of unrecognized glucose dysregulation in patients with schizophrenia receiving conventional antipsychotic treatment.
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