Despite a potentially fatal blow to the first inhaled insulin, this or other painless forms of insulin therapy might still find success.

Only about a year after the inhaled insulin powder Exubera became available, Pfizer Inc. announced in October 2007 that it would stop marketing the medication because of poor sales. Nektar Therapeutics, the California company that developed Exubera, indicated it might seek another marketing partner so that the drug could remain available, but it acknowledged obstacles including high costs.

Among the reasons cited by some patients and doctors for Exubera's unpopularity: the inconvenience of the large inhaler, more waste and greater expense than syringe injections, concerns about possible long-term effects on lung function, reluctance of insurance companies to pay for recommended lung tests, and the need of many patients to continue injecting long-acting insulin.

Still, research continues on other forms of inhaled insulin. These brands may avoid the objections that hurt Exubera. For example, Generex Oral-lyn is a fine insulin spray using a small, hand-held aerosol applicator. Instead of going to the lungs, this liquid is absorbed into the bloodstream through the lining of the mouth. Oral-lyn's manufacturer, a Canadian biotech company, says the drug is already available in Ecuador and has received regulatory approval in India, which has the world's largest diabetic population.

Several other companies are in middle and late stages of developing orally or nasally inhaled insulins that also use a small device. And some scientists are working on other noninvasive forms of insulin delivery, including pills, drops, chewing gum and skin patches. It could take years before such innovations become available to diabetic patients, and some may never prove feasible.