Abstract
The lung is an attractive organ to administer proteins and peptides, which are poorly absorbed from the gastro-intestinal tract. Adding an absorption enhancer is a promising method to increase systemic bioavailability of inhaled peptides and proteins. A combination of insulin powder and citric acid powder showed improved hypoglycemic activity without deteriorating effect of citric acid on insulin stability. Spray drying is a useful and widely applied technique to prepare powders for inhalation. Supercritical fluids have recently been applied for producing powders for inhalation. Selecting operating conditions and adding proper additive such as sugars would produce hollow porous particles, which are easily dispersed and avoid phagocytic clearance in lung, with maximized chemical and physical stability.
