The drug, olanzapine (trade name Zyprexa), belongs to a relatively new family of medications called atypical antipsychotics, which are used to treat schizophrenia, paranoia and manic-depressive disorders. Other drugs in this class include clozapine, risperidone, quetiapine and ziprasidone.
The researchers found metabolic abnormalities ranging from mild blood sugar problems to diabetic ketoacidosis and coma in patients who had been prescribed olanzapine, most of whom were otherwise not known to be diabetic. Diabetic ketoacidosis (DKA) is a serious condition in which a person experiences an extreme rise in blood glucose level coupled with a severe lack of insulin, which results in symptoms such as nausea, vomiting, stomach pain and rapid breathing. Untreated, DKA can lead to coma and even death.
"While our report does not prove a causal relationship between the drug and diabetes, doctors should be aware of such potentially adverse effects," said P. Murali Doraiswamy, M.D., a psychiatrist at Duke and co-author of the study. "We've found cases where patients had some very serious problems associated with olanzapine, and at least 23 of them died."
The findings appear in the July 2, 2002 issue of Pharmacotherapy. The research was self-supported by the authors.
Doraiswamy and Elizabeth A. Koller, M.D., lead author of the study and a medical officer at the FDA, queried the FDA MedWatch Drug Surveillance System, MEDLINE (a biomedical database) and selected abstracts from national psychiatry meetings over a period of eight years and identified 289 cases of diabetes in patients who had been given olanzapine. Of the 289 cases of diabetes linked to the use of olanzapine, 225 were newly diagnosed cases. One hundred patients developed ketosis (a serious complication of diabetes), and 22 people developed pancreatitis, or inflammation of the pancreas, which is a life-threatening condition. There were 23 deaths, including that of a 15-year-old adolescent who died of necrotizing pancreatitis, a condition where the pancreas breaks down and dies. Most cases (71 percent) occurred within six months of starting the drug and many cases were associated with moderate weight gain.
"The average age of adults showing signs of diabetes after taking olanzapine was about 10 years younger than what is generally seen in the community," said Doraiswamy. "The younger age at onset plus the number of serious complications and the improvements reported when the drug was stopped all suggest a link to the disease. However, until we know if there are risk differences among drugs in this class, it is important for physicians to watch all patients receiving this medication for signs of diabetes so that it can be detected quickly and managed."
The study merely suggests an association between the drug and diabetes, said Doraiswamy. Further studies are needed to offer more conclusive evidence of a direct causal relationship. If future studies confirm the findings, he said that perhaps the FDA should consider including a stronger warning label for these drugs.
"The numbers are still sketchy since many adverse reactions are not reported to the FDA and we don't have a good handle on how many people have actually received these drugs," he cautioned. "Atypical antipsychotics can be life saving medications, but we need to learn more about their long-term side-effects. I think this should be a high priority for investigation."
Doraiswamy was part of a team from Duke that first reported a link between the antipsychotic drug clozapine and the development of diabetes in a 1994 issue of the American Journal of Psychiatry. Last year, Koller reported in the American Journal of Medicine that the FDA had received 384 reports of diabetes associated with the drug clozapine. According to the researchers, many cases of diabetes have also been reported with other antipsychotic drugs.
Doraiswamy has previously received funding and consulting fees from all companies that currently manufacture antipsychotic medications, including Eli Lilly and Company, the manufacturer of Zyprexa.