Members of the FDA's Endocrinologic and Metabolic Drugs Advisory Committee questioned the makers of the inhaled insulin on its effects on the lungs, and whether it presented a long-term safety hazard for diabetics who used it.

The developers of the drug, called Exubera, touted it as a way to persuade diabetics who are reluctant to take injections to get insulin. The insulin is being developed by Pfizer, Sanofi-Aventis and Nektar Therapeutics.

Drug company representatives proposed to conduct studies on the long-term effects of the drug until 2019.

"We understand the need to assess the long-term effects on pulmonary function," said Dr. Neville Jackson of Pfizer.

Small Decrease in Breathing Capacity

Other concerns about the drug include whether it is safe and effective on people who smoke or have lung disease, according to documents released Wednesday by the Food and Drug Administration.

The FDA's committee was expected to 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.

During drug trials, researchers found that inhaled insulin was generally as effective as injections in controlling blood sugar levels. However, some patients who took inhaled insulin complained of coughing and a small decrease in breathing capacity.

Linked to Obesity

It is estimated that more than 18 million people in the United States have diabetes, although some do not know it. Most have Type 2, a condition linked to obesity that occurs when the body cannot effectively use the insulin it makes. Sometimes this can be treated with pills instead of injections.

Fewer than 10 percent have Type 1, a disorder in which the immune system attacks insulin-producing cells in the pancreas. This is sometimes called juvenile diabetes.

The number of people in the United States who have diabetes is believed to have tripled in the last quarter-century.

Inhaled insulin could be used to manage blood sugar levels for people with either type who need insulin injections before meals. It wouldn't replace longer-acting insulin injections people with Type 1 diabetes need to take in the morning or before bed, according to FDA documents.

On Friday, the advisory committee will consider another Type 2 diabetes treatment, muraglitazar, developed by Bristol-Myers Squibb. Tablets would be sold under the trade Pargluva and would control blood sugar levels.