Particulate Design of Dry Powder Inhalation by a Novel Supercritical Freeze Granulation

In the particulate design for dry powder inhalation (DPI), the drug particles are required to have a good flowability in handling and dispersibility in delivering the drug to the lung in order to effectively treat pulmonary and systemic diseases. In this study, the preparation process of drug particles for DPI using a novel supercritical carbon dioxide freeze granulation based on the rapid expansion of supercritical solutions (RESS process) has been developed. When a drug dissolved into supercritical carbon dioxide is sprayed through a nozzle, frozen carbon dioxide lumps are generated due to the rapid temperature drop (i. e., Joule-Thomson effect), resulting in the granulation of fine drug particles. The granules prepared under the conditions of lower temperatures and higher pressures of supercritical carbon dioxide, in which more frozen carbon dioxide lumps are generated, have a good flowability and dispersibility because of the increased granule size and the decreased bulk density.