The Food and Drug Administration is delaying a final decision on the first inhalable form of insulin (search) for three months while it reviews chemistry data on the diabetes (search) treatment.

The agency's decision on whether the drug could be marketed to the public had been expected this week. The drug companies that developed the treatment said Friday the FDA notified them of the extended review.

Last month, an FDA advisory committee twice voted 7-2 to recommend that the agency approve the drug and inhaler device for sale in the United States. The separate votes were for each of the two major types of diabetes. The FDA usually follows the recommendations of its advisory committees, but is not required to.

Developers Pfizer, Sanofi-Aventis and Nektar Therapeutics promoted the drug as a convenient alternative to the injections millions of diabetics must take several times daily. It would be marketed under the name "Exubera."

The companies said the FDA wanted to review "additional technical chemistry data" they submitted. They did not provide details.

Advisers who voted to recommend inhaled insulin said its potential benefits outweighed certain problems, most notably whether the effects of the drug on people with lung disease had been fully studied.

Other advisers worried doctors and people with diabetes may not be properly trained in the use and maintenance of the inhaler device. Drug company representatives suggested that the inhaler was not any more complicated than the injections many diabetics now use.

Also this week, developers of another drug to help diabetics control blood sugar levels as well as cholesterol said they are unsure whether they will continue to pursue the treatment after the FDA sought additional safety data about it.

Bristol-Myers Squibb, which developed the pill along with Merck, said the studies required to obtain that data could take up to five years to perform. The drug, muraglitazar, would be marketed under the name Pargluva.

The FDA and some doctors who examined company data from drug trials raised concerns that the treatment could be associated with heart problems.

Bristol-Myers Squibb, based in New York City, released a statement Thursday saying it "will continue discussions with the FDA and will consider a range of options including conducting additional studies or terminating further development of muraglitazar."

Last week, the companies said the FDA had issued them an letter saying the drug was approvable if the companies met certain conditions, but the agency's request for more heart safety data had not been made public until Bristol-Myers Squibb issued its statement Friday.

The drug had appeared headed for the market after members of the FDA's Endocrinologic and Metabolic Drugs Advisory Committee voted 8-1 to recommend FDA approval of the drug to treat Type II diabetes, the most common form of the condition, when used alone. The FDA usually follows the advice of its committees but is not required to do so.

The Journal of the American Medical Association last week published an analysis by heart researchers that found twice as many deaths and cardiovascular problems in diabetic adults taking the drug Pargluva as those on dummy pills or a competing drug.

About 18 million people in the United States are thought to have diabetes, although many do not know it. Untreated diabetes can lead to blindness, loss of limb function, even death.

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.