LUNG PENETRATION PROFILES: A NEW METHOD FOR ANALYSING REGIONAL LUNG DEPOSITION OF INHALED CONTROLLED RELEASE FORMULATIONS

摘要

In recent years, there has been considerable interest in the development of controlled release formulations for administration via the inhaled route (1). The majority of drugs given by inhalation and intended for sustained release should be delivered preferentially to the alveolated regions located in the lung periphery. As a result, it is important to be able to quantify both total and regional lung deposition of these formulations. Gamma scintigraphy is a two-dimensional radionuclide imaging method, which can be applied to the evaluation of new controlled release drug delivery systems administered by the inhaled route. Formulations are usually radiolabelled with ~(99m)Tc, and the drug distribution in the lung is quantified by gamma camera imaging. Regional lung deposition patterns are quantified by dividing the lungs into a series of computer-generated regions of interest. A commonly used algorithm (2) divides the lungs into three box-shaped regions and allows differences in regional lung deposition resulting from changes in particle size, inhalation mode and airway patency to be detected (3). However, division of the lungs into only three regions does not provide a detailed analysis of the distribution pattern within the lungs, and use of regions which conform to the shape of the lungs would be more desirable. In order to address these problems, we have developed a novel form of regional lung analysis, which is described below.