Delivery of insulin via the pulmonary route can potentially provide the benefits of bolus insulin therapy without injections. Pulmonary delivery of insulin uses the well-vascularized, highly permeable alveoli of the lungs as the port of entry for macromolecules. Several formulations of inhaled insulin are in clinical trials or awaiting regulatory approval. Skyler et al.93 provided the proof-of-concept study that illustrates the efficacy of mealtime use of inhaled insulin in individuals with T1DM. Glycemic control was similar in subjects receiving preprandial inhaled insulin plus subcutaneous ultralente insulin at bedtime (HbA1C 7.9% at 12 weeks) or a usual insulin regimen of two to three injections per day (HbA1C 7.7%). Similarly, Cefalu et al?4 showed similar efficacy of inhaled insulin in individuals with T2DM whose treatment with combination oral agents had failed. In both these studies inhaled insulin was well tolerated without adverse pulmonary effects. However, due to its inefficient absorption, approximately 10-fold higher doses of insulin must be administered to achieve a therapeutic response. Data concerning long-term efficacy and safety are currently being collected.
Another alternative insulin delivery approach uses a metered-dose inhaler to direct fine aerosolized droplets of liquid insulin into the mouth for transmucosal absorption. One such formulation (Oral-lyn) has already received regulatory approval in Ecuador and is currently in phase III clinical trials in the Canada and Europe.
Was this article helpful?