Drug Delivery to the Lung: Permeability and Physicochemical Characteristics of Drugs as the Basis for a Pulmonary Biopharmaceutical Classification System (pBCS)

ABSTRACT

The respiratory tract is currently considered as an alternative to gastrointestinal and dermal drug delivery systems and is used to deliver drugs for respiratory diseases as well as the treatment of non-pulmonary disorders. The first step in drug profiling for delivery via the respiratory tract needs to address intrinsic physicochemical parameters and their impact on or correlation with absorption. Moreover, the more the pulmonary drug delivery shall find acceptance, the greater will be the need for validated test systems, methods, and guidelines for regulatory purposes. The Biopharmaceutical Classification System (BCS) remains the simplest and most common guiding principle for predicting drug absorption, but it is limited to the gastrointestinal tract. This review suggests an extension, the pulmonary Biopharmaceutical Classification System (pBCS), that will take into consideration the specific biology of the lung as well as particle deposition, aerosol physics, and the subsequent processes of drug absorption and solubility. We will describe the steps to be taken to develop a pBCS as well as the compounds that will be used to establish this classification. Furthermore, we will introduce two cellular models with which drug permeability across the pulmonary barrier will be determined as an alternative to the currently and widely used studies with animals.

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