Almost 300 people with type 2 diabetes enrolled in the six-month study, which was conducted by researchers at Baylor University Medical Center.
Half of the participants were randomly assigned to use inhaled insulin before meals plus a single bedtime injection of long-acting insulin. The rest of the group used their traditional insulin injection regimens. Eighteen people left the study for various reasons.
The inhaled insulin comes in a dry-powder delivery system similar to some asthma inhalers. When it hits the lungs, it's absorbed directly into the bloodstream, making it take effect faster than injected insulin.
Like injected insulin, doses of the inhaled insulin can be adjusted to accommodate meal size or on an as-needed basis.
About 20% of the inhaled-insulin patients developed a mild to moderate cough lasting an average of two weeks, but cases declined during the study.
Similar numbers of patients from both groups experienced other adverse effects (126 from the inhaled-insulin group and 118 from the injected-insulin group), including hypoglycemia (low blood sugar). Few cases were severe (six in the inhaled-insulin group and one in the injected-insulin group), and most were related to blood sugar.
Inhaled-insulin participants were significantly more satisfied with their treatment than the injection patients. The study was long enough that the novelty of the inhalation system probably didn't account for the satisfaction gap, say the researchers.
Inhaled-insulin patients also didn't gain weight during the study, while insulin injectors added about 3 pounds.
Diet and exercise were emphasized for all participants, who were instructed to follow a weight-maintaining diet and get 30 minutes of moderate exercise at least three times per week during the study.
Inhaled insulin isn't ready for mainstream use. Long-term safety studies must be done first.
If it becomes available, inhaled insulin may appeal to many patients, making them more likely to control their diabetes, say the researchers.