Particle Engineering for Pulmonary Drug Delivery

With the rapidly growing popularity and sophistication of inhalation therapy, there is an increasing demand for tailor-made inhalable drug particles capable of affording the most efficient delivery to the lungs and the most optimal therapeutic outcomes. To cope with this formulation demand, a wide variety of novel particle technologies have emerged over the past decade. The present review is intended to provide a critical account of the current goals and technologies of particle engineering for the development of pulmonary drug delivery systems. These technologies cover traditional micronization and powder blending, controlled solvent crystallization, spray drying, spray freeze drying, particle formation from liquid dispersion systems, supercritical fluid processing and particle coating. The merits and limitations of these technologies are discussed with reference to their applications to specific drug and/or excipient materials. The regulatory requirements applicable to particulate inhalation products are also reviewed briefly.

Effect of shape of sodium salicylate particles on physical property and in vitro aerosol performance of granules prepared by pressure swing granulation method

The purpose of this research was to investigate the effect of the shape of sodium salicylate (SS) particles on the physical properties as well as the in vitro aerosol performance of the granules granulated by the pressure swing granulation method. SS was pulverized with a jet mill (JM) to prepare the distorted particles, and SS aqueous solution was spray dried (SD) to prepare the nearly spherical particles. The particle size distribution, crushing strength, and pore size distribution of the granules were measured. The adhesive force of the primary particles in the granules was calculated according to Rumpf's equation. The in vitro aerosol performance of the granules was evaluated using a cascade impactor. Both JM and SD particles can be spherically granulated by the pressure swing granulation method without the use of a binder. The size of SD granules was smaller than that of JM granules. Although the crushing strength of the JM and SD granules is almost the same, the internal structures of JM granules and SD granules were found to differ, and the SD particles appear to have been condensed uniformly, resulting in a nearly spherical shape. In the inhalation investigation, the percentage of SS particles of appropriate size delivered to the region for treatment was noticeably higher for SD granules than for JM granules. This finding might be because the adhesive force of the SD primary particles was smaller than that of the JM primary particles in the granules and because the SD granules could be easily separated by air current to obtain the primary particles.

A new agglomerated KSR-592 beta-form crystal system for dry powder inhalation formulation to improve inhalation performance in vitro and in vivo

A new agglomerated KSR-592 (steroid) beta-form needle-like crystals with lactose system for dry powder inhalation (DPI) was developed to improve inhalation performance with Jethaler. The drug agglomerates were prepared by the method of spherical agglomeration in liquid so as to control the particle size and the mechanical strength of agglomerates by changing the agitation speed of the agglomeration system. The agglomerates mixed with lactose particles for the DPI formulation were effectively disintegrated into respirable fine particle in the milling chamber of the device (Jethaler) when inhaled. The DPI formulation with these agglomerates exhibited ideal fluidity and provided a larger fine particle fraction (FPF: 29.7%) than the formulation with agglomerates consisting of alpha-form (plate-like) crystals (24.5%). The air-flow rate of inhalation had no effect on the disintegration properties of these agglomerates, suggesting a reliable inhalation performance in vivo. Further, an in vivo test of the aerosolized KSR-592 (beta-form) crystals having the same particle size distribution as those in the aerosol produced by Jethaler was conducted by means of a dry powder inhalation testing system using Brown Norway rats. Inhaled KSR-592 (beta-form) crystals were found to be uniformly deposited in the lungs of Brown Norway rat sensitized by ovalbumin (OA) and suppressed the increase in eosinophil number in the lungs after OA challenge.