Inhaled Insulin Effective For Diabetes

But Study Raises Concerns Over Long-Term Lung Impact

(WebMD)  Although inhaled insulin is comparable to injected insulin in controlling high blood sugar, its use should be reserved for diabetic patients who cannot or will not use needles, according to a new study.

That's because its long-term safety has yet to be established, says Lisa Ceglia, MD, of the Tufts-New England Medical Center in Boston, a researcher on the study.

"For the time being, the most worrisome concern is the effect inhaled insulin may have on lung function," Ceglia tells WebMD. The review article shows that one of the most common side effects of such therapy is increased coughing and a mild decrease in test scores that measure lung function.

"Are there other things to worry about? Possibly," Ceglia says. "But pulmonary toxicity is the issue we focused on because of the way the therapy is administered."

The findings are published in the November issue of the Annals of Internal Medicine.

Short-Term Trials

Ceglia's team reviewed 16 trials of inhaled insulin involving 4,023 patients with type 1 or type 2 diabetes.

Most of the trials lasted only 12-24 weeks. The longest trial lasted two years. It evaluated Exubera, Pfizer Inc.'s inhaled insulin delivery system. Pfizer is a WebMD sponsor.

In January 2006, Exubera became the first new insulin delivery option to be approved by the FDA since insulin was discovered in the 1920s. Pfizer launched the drug in the U.S. market in September 2006.

"All of the trials were open-label, meaning that the patients knew what they were getting," Ceglia says. None of the trials used the so-called "double-dummy" technique, in which patients receive an inhaler and injections without knowing which one contains insulin.

Although that other technique may have produced more definitive results, it was not used because the trial designers considered it "logistically difficult and cumbersome."

"What these trials were designed to do is prove non-inferiority," says Larry Deeb, MD, president of medicine and science at the American Diabetes Association in Alexandria, Va. Deed was not connected with the study. "All Pfizer had to do was prove that inhaled insulin was as good as subcutaneous insulin, not that it was superior."

Inhaled Insulin Worked

Ceglia's analysis showed that inhaled insulin was "comparable" to injected insulin in controlling blood sugar. Its effects were "just slightly less" than those of injected insulin, Ceglia says.

Though injected insulin had a small advantage over inhaled insulin in reducing blood sugar, the same number of patients on either therapy achieved a benchmark of diabetes control: a hemoglobin A1c level of less than 7 percent.

"Clearly, inhaled insulin is not an improvement over subcutaneous insulin, a drug [with] which we've had 80 years of experience," Deeb tells WebMD. "Doctors should tell patients who are already doing well on subcutaneous insulin that they shouldn't expect to do any better if they switch to inhaled insulin."