According to the American Diabetes Association, 8.3% of the population has diabetes, making it a pretty common ailment. A vast majority of those cases fall into the type 2 class that typically develops in adults.

Type 2 diabetes is usually a relatively slowly progressing disease. Unlike type 1 diabetes, where patients require insulin initially, type 2 diabetics start off with unhealthy-but-manageable blood sugar levels, affording time for doctors to intervene with lifestyle changes -- diet and exercise -- as well as drugs to keep blood sugar levels in check.

The first treatment that almost every type 2 diabetetic gets is merformin, a drug originally brought to market by Bristol-Myers Squibb (NYSE:BMY) as Glucophage, which has long since been available as a generic.

It isn't entirely clear how metformin acts, but the drug ultimately suppresses blood sugar production in the liver and increases insulin sensitivity, which can lower blood sugar levels further.

Fewer pills is better
Metformin is typically taken twice a day, which is less convenient than a daily pill, so a few companies have developed extended-release tablets -- Bristol's Glucophase RX, Shionogi's Fortamet, and Santarus' (NASDAQ:SNTS) Glumetza -- that only have to be taken once a day. The slow release can also reduce some of the side effects seen in patients that take the twice daily version.

Despite the cheap competition from twice-daily generics, Santarus managed a 33% year-over-year increase in sales of Glumetza. It's unlikely to become a blockbuster, but $41.5 million in quarterly sales isn't too shabby for a small specialty pharma. Shares of Santarus have tripled over the last year.

Metformin+
Since many type 2 diabetics start on metformin, many branded drugs now come as combination products containing metformin. The idea is simple: If merformin is working, but not completely controlling blood sugar levels, adding another drug could help. And offering it as a single pill makes it easier for patients.

Brand Name Drug

Combined With Metformin

Company

Januvia

Jaumet/Janumet XR

Merck (NYSE:MRK)

Actos

ActoPlus Met/ActoPus Met XR

Takeda Pharmaceuticals

Tradjenta

Jentadueto

Boehringer Ingelheim and Eli Lilly

Nesina

Kazano

Takeda Pharmaceuticals

Onglyza

Kombiglyze XR

Bristol-Myers Squibb and AstraZeneca 

Avandia

Avandamet

GlaxoSmithKline

Source: Drugs@FDA.

There used to be a competitive advantage to having a metformin combination product, but now that almost every diabetes drug is available as a combination, that's vanished. The main competition now comes from the underlying branded product, where Merck's (NYSE:MRK) Januvia/Janumet is leading the pack after side effects derailed Actos and Avandia.

The other consideration is whether the metformin is the standard twice-daily version, or available as a once-daily extended release, usually designated as XR. Januvia, Tradjenta, and Onglyza, for example, are all in the same class of drugs called DPP-4 inhibitors. But only Januvia and Onglyza are available as a combination with extended-releases metformin, making it harder for Trajenta/Jentadueto to compete.

Fool contributor Brian Orelli has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.