People with type 2 diabetes taking the drugs Januvia or Byetta might have an increased risk of developing pancreatitis and pancreatic cancer, a preliminary study suggests.
The study also found that Byetta (exenatide) may raise the risk of thyroid cancer.
Although the links aren't conclusive, they merit further investigation, the researchers noted.
"We have raised concern that there may be a link, but we haven't confirmed it," said lead researcher Dr. Peter Butler, director of the Larry L. Hillblom Islet Research Center at the University of California, Los Angeles. "We need to do more work to figure out whether this is real or not."
Both drugs help control blood sugar levels by encouraging production of a hormone called glucagon-like peptide 1 (GLP-1).
Januvia (sitagliptin) and Byetta, an injectable drug, are a new way of treating type 2 diabetes, and they potentially have advantages over older medications, Butler said. But, because these drugs are new, they're "the ones we know least about," he said. "When new drugs come out, the long-term side effects of these drugs are not well understood."
For the study, recently published in the journal Gastroenterology, Butler's team used 2004-2009 information in the U.S. Food and Drug Administration's database on adverse events, which are reported by doctors whose patients use these drugs.
When compared to other treatments, the researchers found a sixfold increase of reported cases of pancreatitis (inflammation of the pancreas) linked to patients taking Januvia or Byetta; a 2.9-fold increase in reported cases of pancreatic cancer among those taking Byetta and a 2.7-fold increase of reported pancreatic cancers among Januvia users.
In addition, they also noted an increase in reported cases of thyroid cancer with Byetta.