It sounded like a diabetic's dream come true: the idea of inhaling insulin rather than injecting it. But Pfizer's Exubera, the first inhaled insulin product on the market, wound up a commercial failure. After that, other companies like Eli Lilly-Alkermes stopped studies of similar products. Such drugs were meant to grab a share of the ever growing market for diabetes drugs, but research found that the inhaled insulin was inferior to injected insulin.

And many people were left wondering whether inhaled insulin would ever again be available.  

"The question now remains whether this route of delivering insulin has been exhausted or if it still remains to be explored," wrote Dr. Satish Garg and William Kelly, BS, from the University of Colorado Denver in an editorial.

Recently, MannKind Corporation filed a New Drug Application with the Food and Drug Administration (FDA) for its Technosphere Insulin. Technosphere is said to be quicker acting than other insulins.

Though many people with diabetes would love to be able to simply breathe in the insulin rather than give themselves a shot, the inhaled form of insulin has been problematic so far, says Dr. Priscilla Hollander, an endocrinologist with Baylor University Medical Center in Dallas. "It just didn't prove as popular and it never seemed to take off," she says. "It took time to teach the patients how to use it. And then there was some question of whether it could have side effects or toxicity."

Insulin, Hollander notes, is a "potent agent," and some experts wondered whether it could even cause lung cancer. "But that was never shown," she explained.

While no inhaled insulins are currently being given to patients, Mannkind's Technosphere is showing promise, she says. "It is much easier to use and there is a market for it," Hollander says.

If it's approved and becomes available for use, the obvious advantage over injections is that it doesn't involve a shot, says endocrinologist Dr. Stuart Weiss, clinical assistant professor at New York University School of Medicine.

It works quickly, which is another plus, he explains. "The problem with insulin injections is that they are slower to come into the bloodstream," Weiss says. "This new inhaled insulin now in development holds promise, and the delivery system is much smaller. It could prove to be a really exciting alternative in the not too distant future."