Treating Type 2 Diabetes with Inhaled Insulin

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The summary below is from the full report titled "Inhaled Human Insulin Treatment in Patients with Type 2 Diabetes Mellitus." It is in the 6 February 2001 issue of Annals of Internal Medicine (volume 134, pages 203-207). The authors are WT Cefalu, JS Skyler, IA Kourides, WH Landschulz, CC Balagtas, S-L Cheng, and RA Gelfand, for the Inhaled Insulin Study Group.

What is the problem and what is known about it so far?

Type 2 diabetes mellitus (adult-onset diabetes) is a disease that interferes with the body's ability to store food, including sugar, and results in high blood sugar levels. The hormone insulin helps the body to store food and to keep blood sugar levels within the normal range. Body tissues in persons with type 2 diabetes are resistant to the effects of insulin. In addition, these patients lack effective insulin levels required to keep their blood sugar levels normal. Some patients can overcome the abnormalities by taking prescription pills, while others need to take insulin injections one or more times daily. Researchers have been exploring ways to give insulin to diabetic patients other than by injection. One alternative is inhaled insulin, whereby patients breath insulin into their lungs by using a special device.

Why did the researchers do this particular study?

To find out whether inhaled insulin works and is safe in the treatment of type 2 diabetes.

Who was studied?

Twenty-six patients with type 2 diabetes who were injecting insulin 2 to 3 times per day for a month or longer but still did not have excellent blood sugar control, despite this stable regimen.

How was the study done?

Patients in the study took a dose of inhaled insulin before each meal and injected long-acting insulin at bedtime. Patients monitored their blood sugar levels at home, and the researchers adjusted patients' insulin doses each week, as needed. The researchers used a blood test called hemoglobin A_1c to measure patients' diabetes control before starting the inhaled insulin therapy and then every month for 3 months. Hemoglobin A_1c indicates how well blood sugar levels have been controlled during the preceding 3 months. To see whether inhaling insulin would cause lung problems, patients performed special breathing tests before and 3 months after starting inhaled insulin.

What did the researchers find?

Patients' hemoglobin A_1c levels improved during the 3 months of inhaled insulin therapy. No patient had a severe episode of low blood sugar, and the breathing tests showed no lung problems.

What were the limitations of the study?

The study did not compare patients taking inhaled insulin with patients who took only insulin injections; it therefore does not tell us that inhaled insulin controls diabetes better than injected insulin. In addition, it is not known whether patients would continue to show improved blood sugar levels or have side effects if they used inhaled insulin for longer than 3 months. Patients in this study were injecting insulin at bedtime in addition to the inhaled insulin taken before meals, so the study does not tell us whether inhaled insulin by itself controls blood sugar.

What are the implications of the study?

Use of inhaled insulin before meals, together with insulin injections taken at bedtime, appears to be an option for treatment of type 2 diabetes.