A small initial decline in function did not appear to progress beyond 3 months.
In previous short-term studies, inhaled insulin caused small declines in lung function. In this industry-sponsored trial, researchers assessed longer-term respiratory effects of inhaled insulin.
Nearly 600 adults with type 1 diabetes were randomized to receive premeal inhaled insulin (Exubera) or premeal subcutaneous short-acting insulin; both groups also received long-acting basal insulin. At 3 months, mean FEV1 had declined by 0.05 liters in the inhaled insulin group and 0.03 liters in the subcutaneous insulin group, a small but statistically significant difference. However, after 3 months (and through 24 months), FEV1 declined at the same rate in both groups. For diffusing capacity, the same pattern was noted — a small initial decline, but no further separation between groups during months 3 to 24. Inhaled-insulin recipients reported cough more frequently than subcutaneous-insulin recipients (38% vs. 13%). Glycemic control was similar in the two groups.
Comment: This study demonstrates that inhaled insulin induces small changes in pulmonary function shortly after the start of treatment. On average, however, the changes do not appear to progress after 3 months. Patients are advised to have spirometry before starting inhaled insulin, after 6 months of treatment, and annually thereafter. Inhaled insulin is not recommended for patients with underlying lung disease and is contraindicated in smokers.
— Allan S. Brett, MD
Published in Journal Watch General Medicine March 29, 2007