Tell me about the diabetes drugs Byetta, Victoza and Bydureon. Can they really help people who have diabetes lose weight? Are there side effects?

Exenatide (Byetta, Bydureon) and liraglutide (Victoza) are taken by injection, similar to insulin, but they're not insulin. These medications are in a class of drugs called incretin mimetics, which improve blood sugar control by mimicking the action of a hormone called glucagon-like peptide 1 (GLP-1). Among other things, these drugs stimulate insulin secretion in response to rising blood sugar levels after a meal, which results in lowering of the blood sugar.

Byetta, Bydureon and Victoza not only improve blood sugar control, but may also lead to weight loss. There are many proposed ways in which these medications cause weight loss. They appear to help suppress appetite. But the most prominent effect of these drugs is that they delay the movement of food from the stomach into the small intestine. As a result, you may feel "full" faster and longer, so you eat less.

Byetta is injected twice daily, and Victoza is injected once a day. Bydureon, a newer formulation, is injected once a week. These drugs do have different effects and side effects to consider.

• Exenatide (Byetta, Bydureon). The most common side effect of exenatide is mild to moderate nausea, which improves with time in most people. Several cases of kidney problems, including kidney failure, have been reported in people who have taken exenatide. Rarely, exenatide may cause harmful inflammation of the pancreas (pancreatitis).
• Liraglutide (Victoza). Some studies have found that liraglutide reduces systolic blood pressure and triglycerides, in addition to improving blood sugar control. The most common side effects are headache, nausea and diarrhea. Clinical studies have also shown that liraglutide may cause pancreatitis.

If you have a personal or family history of medullary thyroid cancer or multiple endocrine neoplasia, you shouldn't use exenatide or liraglutide. Laboratory studies have associated these drugs with thyroid tumors in rats. Until more long-term studies are completed, the risk to humans for developing these types of tumors as a result of using these drugs isn't known.

These drugs are designed for people who have type 2 diabetes. However, a new drug containing a higher dose of liraglutide (Saxenda) was recently approved by the Food and Drug Administration for treatment of obesity in nondiabetics. If you have diabetes and wonder if Byetta, Bydureon or Victoza may be helpful, talk to your doctor.

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