Byetta (exenatide)

Byetta (exenatide) is an injectable medication prescribed for managing blood sugar levels in adults with Type 2 diabetes. Its active ingredient is exenatide and it belongs to the glucagon-like peptide-1 (GLP-1) agonist drug class.

The drug is designed to be used alongside a diet and exercise program and it may be combined with other diabetes medications.

Exenatide, Byetta’s active ingredient, mimics the action of the GLP-1 hormone your intestine releases after eating, and it:

• Stimulates the pancreas to produce more insulin when blood sugar is high.
• Lowers sugar production by the liver.
• Slows down the movement of food from the stomach to the intestine, which slows down sugar absorption.
• Reduces appetite.

The medication is available in prefilled pens with standard microgram dosages of 5 mcg or 10 mcg per injection, and it’s taken twice a day before meals.

Byetta is FDA-approved for Type 2 diabetes management, not for Type 1 diabetes. While it may contribute to modest weight loss for some people, it’s not approved or typically prescribed for weight loss.

Newer GLP-1 drugs, such as Ozempic (semaglutide) and Mounjaro (tirzepatide), have been prescribed for off-label purposes — uses that aren’t FDA approved — such as weight loss.

Yet other diabetes drugs, like Wegovy (semaglutide) and Saxenda (liraglutide), are FDA-approved for weight loss.

Common side effects of Byetta, such as nausea, indigestion and vomiting, are typically mild and go away after the body gets used to the medication. But Byetta may also cause serious side effects such as pancreatitis (inflammation of the pancreas).

“The most common side effects people notice [with GLP-1 medications] are going to be things like nausea, upset stomach, constipation, acid reflux, and sometimes vomiting and diarrhea, especially when first starting the medicine or increasing the dose,” Dr. Lauren Cunningham told Drugwatch.

To avoid common side effects, doctors start people at a lower dose and slowly increase it over time, Cunningham said. These side effects will usually go away after a few days or weeks, but if they bother you or don’t go away, talk to your medical provider.

Serious Side Effects

While most people will only experience mild side effects, Byetta can have serious side effects that affect the pancreas, kidneys and digestive tract that may require additional treatment.

Because acute pancreatitis can be a precursor to pancreatic cancer, it is plausible that Byetta and other GLP-1 drugs could increase the risk of pancreatic cancer. However, most studies so far haven’t found an increased pancreatic cancer risk.

Overall, the science behind serious Byetta side effects such as pancreatitis and pancreatic cancer is mixed, and many studies didn’t find a link to pancreatic cancer.

In 2013, the FDA released a safety warning about unpublished findings that linked GLP-1 drugs, also called incretin mimetics, to pancreatitis and pre-cancerous cells in the pancreas.

This warning also referenced a published study that suggested Byetta use could double the risk of developing acute pancreatitis.

Since the initial FDA warning in 2013, more studies have come out that don’t show an increase in pancreatic cancer.

For example, a 2024 study of 543,595 people published in JAMA found no increased incidence of pancreatic cancer in people who took a GLP-1 drug over seven years.

The FDA also hasn’t found evidence that Byetta and other GLP-1s cause pancreatic cancer.

The initial FDA GLP-1 pancreatic cancer warning in 2013 led many people to file Byetta lawsuits as well as lawsuits against the makers of other diabetes drugs like Janumet, Januvia and Victoza. According to the plaintiffs, these drugs caused them to develop pancreatic cancer, and they weren’t warned about the risk.

In 2013, these lawsuits were grouped together in one large litigation called a multidistrict litigation (MDL). In an MDL, similar claims against the same defendants are grouped together to make litigation more efficient.

Ultimately, the MDL litigation ended in 2021 after the cases were dismissed for good.

The good news for patients is that newer studies haven’t found that Byetta increases pancreatic cancer risk, though the drug still has a warning for pancreatitis. Patients should discuss the risks and symptoms of pancreatitis with their doctor.

Even though pancreatic cancer litigation involving GLP-1 drugs is pretty much over, newer GLP-1 drugs face recent lawsuits for severe stomach problems and a rare vision disorder called NAION.

For example, Ozempic lawsuits say the drug can cause stomach paralysis as well as NAION vision loss. There are similar claims in Wegovy lawsuits, Saxenda lawsuits and Victoza lawsuits.