Purpose: Pharmacokinetic and safety data related to the use of inhaled insulin for the management of diabetes mellitus are discussed. The various pulmonary insulin delivery systems under development are also reviewed.
Summary: Several pharmaceutical companies are developing pulmonary insulin delivery systems. These products fall into two main groups: solution and drug powder formulations, which are delivered through different patented inhaler systems. Exubera, a rapid-acting insulin in powder form, has been studied extensively in patients with type 1 and type 2 diabetes mellitus. The AERx Insulin Diabetes Management System delivers a liquid form of human insulin. Preliminary data indicate that patients converting from insulin injections to this system showed higher compliance to therapy, demonstrated by improved glycemic control. Other pulmonary insulin delivery systems, including ProMaxx, AIR, Spiros, and Technosphere, are also under investigation. In humans, inhaled regular insulin is more rapidly absorbed than insulin from the subcutaneous injection site. The efficiency of inhaled insulin is lower than that of subcutaneous injection because pulmonary delivery of insulin involves some loss of drug within the inhaler or mouth during inhalation. A concern of many clinicians is the possibility of long-term effects from the intraalveolar deposition of insulin within the lung, since insulin is known to have growth-promoting properties. The long-term safety of these products has not been established.
Conclusion: Several inhaled insulin products are under development. If these products receive marketing approval, the pulmonary delivery of insulin may offer patients with diabetes an alternative to repeated insulin injections.