Diabetes therapy trials with inhaled insulin.

Administration of insulin by inhalation was first attempted > 50 years ago. At that time, little was known concerning effective delivery systems and insulin formulations. The recent development of pulmonary delivery systems for the administration of insulin is driven by the reluctance of patients and their providers to initiate insulin earlier in the course of Type 2 diabetes, the desire to reduce the number of daily insulin injections for both Type 1 and 2 patients, and the recent emphasis on intensified glycaemic control including postprandial glycaemic control. The deep lung is a unique mucosal tissue having a surface area of > 100 m2 and is readily accessible both to the external environment and to drug delivery, provided that appropriate conditions are met. There have been four mid- to late-phase pulmonary insulin programmes using modern inhalation devices that will be reported in this paper. The programmes differ in the choice of delivery systems, the formulations of insulin and reported bioavailability, pharmacokinetic and glucodynamic profiles and adverse events. However, all systems successfully deliver insulin to the deep lung and biological effectiveness compares favourably with injected subcutaneous insulins.