Inhaled insulin in patients with asthma and chronic obstructive pulmonary disease

The effect of inhaled insulin in subjects with diabetes and chronic lung disease, such as asthma or chronic obstructive pulmonary disease (COPD), is of particular interest because these diseases are quite common, and it is likely that patients with asthma or COPD who are poorly controlled on oral agents and are reluctant to start subcutaneous insulin would benefit from inhaled insulin to improve their glucose control. Since patients with asthma or COPD have varied pulmonary symptoms and abnormal pulmonary function, it is important to establish the pulmonary safety and efficacy of inhaled insulin in subjects with diabetes and asthma or COPD. Pharmacokinetic and pharmacodynamic studies in non-diabetic subjects with asthma consistently show lower absorption of inhaled insulin and lesser glucose lowering effects by approximately 30-40%, as compared to subjects without asthma. Thus, it would be expected that the dose of insulin required to obtain equivalent glycemic control would be higher by approximately 30-40% in subjects with asthma and diabetes (as compared to subjects without asthma but with diabetes). However, prior administration of a bronchodilator inhaler in individuals with asthma and diabetes reverses airway obstruction and thus may obviate the need for increased insulin requirements. In contrast to patients with asthma, in patients with COPD and diabetes, the absorption of inhaled insulin appears to be variable (higher or lower than in non-COPD subjects). Whether this variability is secondary to differences in inhalation devices or different study populations is not clear at present. Overall, data from the clinical studies indicate that inhaled insulin is effective and well tolerated in subjects with diabetes and chronic lung disease. However, preliminary, limited data from the longer-term clinical studies suggest that there is a marginally greater decline in pulmonary function tests in subjects with asthma/COPD and diabetes compared to subjects with diabetes and no chronic lung disease. Thus, there is a clear need for longer-term studies in subjects with diabetes and chronic lung disease in order to further clarify the safety and efficacy of inhaled insulin in this population.