Issue 174 Item 3 Olanzapine Treatment Associated with a Higher Incidence of Diab

Patients treated with olanzapine for psychosis have a higher risk of developing type 2 diabetes than are untreated patients or those receiving risperidone, quetiapine, or conventional antipsychotics.

That comes from a recent American study sponsored by AstraZeneca Pharmaceuticals, L.P.
Atypical antipsychotic drugs, such as risperidone, olanzapine, and quetiapine, are as effective as conventional antipsychotics in treating symptoms of schizophrenia and related psychoses, but are less likely to cause extrapyramidal side effects. Further evaluation of other potential side effects of these treatments, however, is still necessary.
A number of studies have observed an increased risk of type 2 diabetes with the use of atypical antipsychotics, particularly with olanzapine and clozapine. However, analysis often did not evaluate whether the patients had a confirmed diagnosis of diabetes or were just examined for diabetes. Additional studies with a more conservative approach are therefore needed.

Frank Gianfrancesco, PhD, with HECON Associates, Montgomery Village, Maryland, United States, and colleagues evaluated the relationship between antipsychotic treatment and type 2 diabetes.

The retrospective study analysed claims data from an insurance company representing almost 2 million people. From this database, patients with reported psychosis were identified that were either treated (6,582 patients) or not treated (10,296 patients) with antipsychotic medications, including risperidone, olanzapine, quetiapine, and conventional antipsychotics. The incidence of type 2 diabetes in these patients was determined by prescription claim for anti-diabetic medication or insulin.

Overall, 117 patients with psychoses were treated for diabetes, 30 of which were concurrently receiving anti-psychotic medications. Within this subgroup, olanzapine had the highest percentage of cases of diabetic treatment, followed by conventional antipsychotics.

Further analysis revealed that compared to untreated patients, those receiving olanzapine had a 3% higher likelihood of type 2 diabetes with one month of treatment and a 42.6% increased chance with 12 months of treatment. However, patients receiving quetiapine or conventional antipsychotics had a similar risk of developing diabetes as those who were not treated, and those receiving risperidone showed a slightly lower risk (OR 0.6).

The study also revealed that patients with bipolar disorder and major depression had a significantly lower risk of type 2 diabetes than patients with other psychoses. Furthermore, a higher risk of diabetes was observed in patients concomitantly using beta-blockers.

Dr. Gianfrancesco concludes that in this study, which used more restrictive criteria for type 2 diabetes than previous studies, "patients treated with olanzapine alone were shown to face higher odds of type 2 diabetes than patients with psychosis untreated with antipsychotics." He further adds that "with regard to the risk of type 2 diabetes, [risperidone and quetiapine] appear to be safer than olanzapine." J Clin Psychopharmacol 2003;23:4:328-35

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