One of the fastest growing medication classes for people with type 2 diabetes are the incretins. Injectable like insulin but without two of insulin’s less desirable side effects, weight gain and risk of hypoglycemia, they are becoming a drug of choice for people who still have functioning beta cells and are overweight, but whose control has deteriorated so appreciably that they could be started on a basal insulin.
Incretins can’t be substituted for insulin—if your beta cells are completely drained they won’t work as well because one of their major effects is to increase the amount of insulin available when blood glucose is high. They are not approved as weight loss drugs, but they do stimulate weight loss as a side effect of the drug.
All of the incretins on the market work in pretty much the same way. They mimic a hormone we have in our bodies called Glucagon-like peptide-1 (GLP-1.) GLP-1 boosts the action of insulin by enhancing insulin synthesis and beta cell expansion. It also improves beta cell survival. Hypoglycemia is avoided because GLP-1 is secreted only when blood glucose levels are high.
The synthetic form of GLP-1 is called exenatide. Exenatide has a longer half-life than the natural version so it keeps insulin around longer. It slows gastric emptying so glucose doesn’t enter the bloodstream as quickly, a benefit for people with type 2 diabetes who have lost their first phase insulin response. In addition, it improves first phase insulin response and reduces excess output of glucose from the liver. Although the exact mechanism is unknown, (they do know it works through the brain) exenatide helps people to reduce their food intake. Research has shown that there is a reduction in consumption that is unrelated to its potential side effect of nausea.
The oldest of them, Byetta®, has been on the market for seven years now. It is injected twice a day up to an hour before meals. Victoza®, a competitor brand, is taken once a day without regard to meals. And now there is a third version available, approved by the Food and Drug Administration (FDA) in January of this year , called Bydureon® which is injected only once per week, and (like Victoza®) can be taken without regard to meals.
So why would anyone want to take two injections per day if they could take one only one a week? One possibility is that Byetta® has a longer track record; it’s been on the market longer and its warts are already known. Bydureon® is the new kid on the block and even though it is made out of the same stuff as Byetta® its new formulation means that it could react in the body in ways that Byetta® doesn’t.
Blood glucose target is another. Byetta® is best at reducing post-prandial blood glucose numbers post breakfast and dinner whereas Victoza® has the largest impact on fasting and lunch values. The closer you are to your target A1C the more influence post- prandial numbers have on getting you closer.
The possibility of prolonged side effects makes some people choose one over another. When you take a drug twice or once a day you can easily stop it if you suffer any untoward consequences. It isn’t as easy with a once-a –week formulation. Being nauseous for a whole weak isn’t a fun prospect. (But many people don’t have any side effects.)
Price is another consideration: new drugs are usually priced higher by insurance companies even if they do the same thing as drugs already on the market. Look at the market for heartburn medication—most of the drugs being marketed are versions of the proton-pump inhibitors first developed in prior decades. They may have a few more bells and whistles but their overall mechanism of action is the same.
If this blog post interests you, you should talk to your doctor about the possibility of starting on an incretin.