[Inhaled insulin: a new route in the optimisation of glucose regulation]

The lungs constitute an attractive route for the administration of insulin in view of their large surface area and the permeability for proteins. Inhaled insulin may greatly reduce the daily nuisance of subcutaneous injections for millions of patients. The acceptance of insulin therapy may therefore be increased, so that better metabolic control can be achieved. For optimal efficacy it is essential that the insulin be precipitated in the alveoli and it is precisely the reproducibility of this process that is variable and dependent upon a variety of factors. Thus, the properties of the particles, technique of respiration, administration system and the presence of pulmonary disease (smoking) all play a role. The pharmacokinetics make inhaled insulin suitable for preprandial administration: the absorption is very rapid, so that it can be taken a very short time before meals. The duration of action, however, is short, so that the use of long-acting insulin usually remains necessary. The biological availability of inhaled insulin is < 20%, so that the required dose is larger. The long-term effects of the intra-alveolar administration of insulin and its immunological consequences are still insufficiently clear, although no permanent negative effects have been demonstrated so far. Partly in view of the favourable pharmacodynamic properties, the use of inhaled insulin is an attractive therapeutic option, not only for the group of patients with a fear of injections but for all diabetics that require insulin therapy.