The effect of clozapine on blood glucose metabolism

The aim of this prospective study was to examine the effect of clozapine on blood glucose metabolism compared with haloperidol. Oral glucose tolerance tests were taken every week for 8 weeks to assess the prevalence of diabetes mellitus, impaired glucose tolerance and glycemic peak delay in 19 patients of the clozapine group compared with 15 patients of the haloperidol group. There were two dropouts in the clozapine group and five in the haloperidol group. Finally 17 patients in the clozapine group and 10 patients in the haloperidol group participated in this study. In the clozapine group, six patients (35%) had impaired glucose tolerance, and seven patients (41%) had glycemic peak delay. In the haloperidol group, no patient (0%) had impaired glucose tolerance, and one patient (10%) had glycemic peak delay. None of either group developed diabetes mellitus. In conclusion, the clozapine group had more impaired glucose tolerance and glycemic peak delay than the haloperidol group. However, this difference did not achieve statistical significance (p = 0.056, p = 0.189). Copyright 2001 John Wiley & Sons, Ltd.