As I indicated in another recent post, Ask Your Physician About Non-insulin Injectable Drugs For Treating Diabetes, there are several different types of injectable medications to treat type 2 diabetes (T2D).
The first, of course, is insulin. Insulin has been available since the 1920's, and always works to decrease blood glucose levels (BGLs). But its side effects of hypoglycemia and weight gain, plus the inconvenience of injections and the wide variability in the doses that are needed to control BGLs, have resulted in a bad rap. Sadly, many patients (and too many non-specialist physicians) are unwilling to start insulin therapy despite the fact that the drug will always lower BGLs.
The next injectable to become available, pramlintide (brand name Symlin), has been around since 2005. It's approved in the US only for people who are already taking insulin, and who have "failed to achieve desired glycemic control despite optimal insulin therapy". That's a pretty small group of people, and to make matters worse, it should be given at mealtimes (when insulin is also frequently given), has to be given as a separate shot (sorry, you can't mix it with your insulin shot), and it has a definite risk of severe hypoglycemia, especially if the insulin dose isn't slashed back when it is started. I think that the role of this medication in treatment of T2D is very limited, and apparently the market agrees -- sales have been dismal, and, as far as I know, no other manufacturer has tried developing a "me-too" version of pramlintide.
The most extensive class of injectable medications for diabetes is a much more complicated story. It started with a single drug that was also approved in 2005, exenatide (brand name Byetta). Exenatide was the first drug in the class called "glucagon-like peptide-1 receptor agonists" (or GLP1 agonists), and has a side effect that may explain part of its success: weight loss. There's been lots of competition from other GLP1 receptor agonists, such as once-daily liraglutide (Victoza) and more recently, others named lixisenatide (Lyxumia, available in Europe but not in the US) and once-weekly albiglutide (Tanzeum). This is despite some concern over the safety profile of these drugs, as they may cause pancreatitis or other pancreatic problems, and they might cause an unusual form of thyroid cancer, called medullary thyroid carcinoma. They also frequently cause nausea and other gastrointestinal side effects, which usually resolve over time. But overall, the GLP1 agonists are definitely worthy of consideration for treating T2D, especially in folks who are on multiple medications and fearful of insulin or hypoglycemia, or who want to lose weight and have failed despite trying.