Olanzapine is effective for schizophrenia management; however, it is contraindicated in diabetes patients. In addition, olanzapine is useful for treating nausea and vomiting, such as in the case of chemotherapy-induced nausea and vomiting (CINV). Therefore, we hypothesized that the contraindicated prescription of olanzapine likely occurs among cancer patients with diabetes, especially by non-psychiatric physicians. Hence, we conducted a nationwide survey to elucidate the situation of such contraindicated prescriptions and the associated risk factors. We extracted the data of patients who were newly prescribed olanzapine between April 2015 and March 2017 from the health insurance claims database developed by JMDC, Inc., Tokyo. The patients who were prescribed contraindicated olanzapine were defined as those who were prescribed olanzapine after a diagnosis of diabetes and diabetes drug prescription. In all, the data of 7181 patients were analyzed. We evaluated the proportion of diabetes patients who were prescribed contraindicated olanzapine from among those who were prescribed olanzapine. Furthermore, we investigated the background of patients who were prescribed olanzapine for information such as olanzapine prescribers and history of cancer chemotherapy. In all, 100 diabetes patients (1.39%) were prescribed olanzapine. In these patients, the frequency of olanzapine prescription was higher by non-psychiatry/neurology physicians than by psychiatry/neurology physicians (3.25 and 0.85%, respectively). Additionally, all olanzapine prescriptions in cancer chemotherapy-treated diabetes patients were issued by non-psychiatry/neurology physicians. Thus, our study revealed there were diabetes patients who were prescribed olanzapine. Additionally, olanzapine for CINV management was more likely to be a contraindicated prescription.
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