According to documents released by the Food and Drug Administration, chief concerns involve long-term effects on the lungs, as well as the safety of its use among smokers or sufferers of lung disease.
The inhaled insulin, known as Exubera, could help diabetics reluctant to take injections. The drug is being developed by Pfizer, Sanofi-Aventis and Nektar Therapeutics.
On Thursday, the FDA's Endocrinologic and Metabolic Drugs Advisory Committee will consider whether to recommend the drug to government regulators for approval. The FDA usually follows the recommendations of its advisory committees, but it isn't required to do so.
During tests, researchers found inhaled insulin was generally as effective as injections in controlling blood sugar levels. Some patients who took the drug, however, complained of coughing and slight shortness of breath.
Estimates indicate more than 18 million people in the U.S. have diabetes, though some do not know it. Most suffer Type 2, a condition linked to obesity that occurs when the body does not effectively use the insulin it produces. On occasions, this can be treated with pills rather than injections.
Fewer than 10 percent suffer Type 1, which occurs when the immune system attacks insulin-producing cells in the pancreas; this is also known as juvenile diabetes.
The number of diabetes sufferers in the U.S. is believed to have tripled in the last 25 years.
