Pulmonary Drug Metabolism, Clearance, and Absorption

H.D.C. Smyth and A.J. Hickey (eds.), Controlled Pulmonary Drug Delivery, Advances in Delivery Science and Technology, DOI 10.1007/978-1-4419-9745-6_2, © Controlled Release Society 2011 Abstract Delivering therapeutic agents to the lungs requires a deep understanding of the kinetics and dynamics of drugs in this biologically and physiologically complex system. In this chapter these concepts are discussed and include drug dissolution rates in the airways, physical clearance mechanisms of the mucociliary escalator and cough, alveolar macrophage clearance, pulmonary metabolism, and pulmonary absorption. Finally, these aspects are considered together with drug and formulation aspects as determinants of duration of effects of inhaled products. The mechanisms of elimination of drug activity in the lungs by the various clearance processes described here are important factors to consider both in the development of new drugs and in understanding the relative merits of existing therapies.