Preparation of macromolecule-containing dry powders for pulmonary delivery

Drug delivery by inhalation is routine for the treatment of local pulmonary conditions like asthma, cystic fibrosis, and chronic obstructive pulmonary disease. Only recently, though, has the inhalation route been considered for administering drugs for systemic diseases. The pulmonary route is attractive for several reasons. It is non-invasive, it avoids first-pass metabolism, and it allows drug absorption from a large, highly vascularized surface area. However, consistent delivery to the deep lung requires drug particles within a very narrow size range. Several particle engineering approaches have been used to produce dry powders that will reach the alveolar space. Some of these methods, such as spray drying from solution, the formation of drug-containing liposomes, and the controlled crystallization of particles, are described here.