For the past 80 years sub cuteneous (s/c) injection has been the only way of delivering insulin to diabetes patients. This is even after knowing that s/c insulin administration does not lead to optimal pharmacodynamic properties (the absorption into blood stream is not rapid) of insulin.
Immediately after the discovery of insulin, various routes for its administration are studied with great details in order to reduce the pain associated with s/c injection and to improve the pharmacodynamic properties of applied insulin. Dermal insulin application does not result in adequate transfer of insulin across the highly efficient skin barrier. The �insulin tablet� is also a distant reality due to digestion process and lack of a specific peptide carrier system in the gut. Nasal insulin application has shown rapid absorption of insulin through nasal mucosa. However, the relative bioavaibility is low and it required the use of absorption enhancers. Even then till now it appears that the pulmonary application of insulin is likely to be the first alternative route of insulin administration to become available within next few years.
Due to the extensive progress made in the development of pulmonary insulin application it can be predicted that the pre-prandial inhalation of insulin will become the first alternative to s/c injections in the near future. The clinical-experimental studies show that the pharmacodynamic effects of inhaled insulin are at least as good as those with s/c injection of regular insulin. The clinical trials have indicated that inhalation of insulin might prove especially beneficial for post prandial insulin substitution in those patients with type 2 diabetes, who are reluctant to take injections and therefore continue to take oral agents, even if insulin therapy is indicated.
The critical questions regarding the long-term consequences of the inhalation of insulin are the development of insulin-antibodies, changes in lung function and lung safety which were raised during the clinical development appear to be answered by appropriate long-term studies.
The cost-benefit issues must also be considered, particularly in light of the growing financial burden of type 2 diabetes fir the healthcare systems. The premium costs of any new therapeutic option must be considered in the context of the potential optimization of metabolic control, avoidance of hypoglycemic events and the prevention of long-term complications. Appropriate studies investigating these aspects are missing. In summary, it seems as if, after several decades of research, for the first time a feasible alternative route for insulin administration is within reach.