Clozapine Associated With Risk of Hyperglycemia and Diabetes


April 08, 2004

April 8, 2004 — Clozapine (Clozaril) is associated with a risk of hyperglycemia and diabetes, according to an alert released yesterday by MedWatch, the U.S. Food and Drug Administration (FDA) safety information and adverse event reporting program. The FDA and Novartis notified healthcare professionals last week of revisions to the warnings section of labeling for clozapine that describe the increased risk.

The FDA based its labeling change decision on a review of recent data related to the use of atypical antipsychotics and hyperglycemia. Although precise estimates are not available, epidemiologic studies suggest an increased risk of treatment-emergent hyperglycemia-related adverse events in patients using these drugs. In March, Eli Lilly and Co. revised labeling for its atypical antipsychotic olanzapine (Zyprexa).

According to a letter to clinicians from Novartis, the relationship between atypical antipsychotic use and hyperglycemia is not fully understood, and the link is confounded by the possibility of increased background risk of diabetes mellitus in patients with schizophrenia as well by the increasing incidence of diabetes in the general population.

The FDA recommends that patients with diabetes starting on atypical antipsychotic drugs be monitored regularly for worsening of glucose control. Patients with risk factors for diabetes should undergo fasting blood glucose testing at the beginning of treatment and periodically thereafter.

All patients receiving atypical antipsychotics should be monitored for symptoms of hyperglycemia (polydipsia, polyuria, polyphagia, and weakness). Those developing these symptoms during treatment should undergo fasting blood glucose testing.

In some cases, hyperglycemia has resolved upon discontinuation of the atypical antipsychotic, while in others use or continuation of anti-diabetic treatment was required.

Healthcare professionals should report all serious adverse events suspected to be associated with use of clozapine to Novartis Pharmaceuticals Corporation, One Health Plaza, East Hanover, NJ, 07936, or by phone at 1-888-NOW-NOVARTIS (1-888-669-6682), or the Internet at

Adverse events may also be reported to the FDA MedWatch program at 1-800-332-1088, by fax at 1-800-332-0178, by mail to MedWatch, HF-2, FDA, 5600 Fishers Lane, Rockville, MD 30867, or via the Internet at

Reviewed by Gary D. Vogin, MD


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as: