The effect of clozapine on glucose metabolism.

Although there have been several reports that clozapine precipitated hyperglycemia and diabetic ketoacidosis in some patients, the mechanism by which clozapine impairs glucose metabolism is not known. This study investigated the effect of clozapine on glucose metabolism in six schizophrenic patients while they were free of medication and receiving 200 mg/d and 450 mg/d of clozapine. Clozapine increased mean levels of blood glucose, insulin and C-peptide. It is possible, based on these findings, that the glucose intolerance was due to increased insulin resistance.