Particle design of Wogon extract dry powder for inhalation aerosols with granulation method

Aerosolization of Wogon extract powder (WEP) is difficult due to its strong adhesiveness to the inhalation device (Spinhaler(R)) on emitting. To improve inhalation property, WEP was granulated by slugging, tumbling and agitation methods. The inhalation properties were measured in vitro with a cascade impactor and a twin impinger. The inhalation behaviors of granules were determined by granulation method employed and inhalation conditions such as inhaled air flow rate. It was found that a key factor determining the inhalation property was the mechanical strength and the particle size of the granules. Soft granules were easily dispersed into air stream and were disintegrated to fine respirable particles. Whereas they adhered strongly to the inside wall of the device on inhalation. Consequently, a proportional correlation between the residual fraction in the inhalation device and the respirable fraction (RF) of the cascade impactor or the twin impinger was observed. A new inhalation index, effective index (ET), was proposed to evaluate the overall inhalation property by taking the residual fraction and RF into account. Tumbling granulation method provided the largest EI, and improved the inhalation property of original WEP. The Els of granules prepared by tumbling granulation and slugging granulation with lower compaction pressure were larger than that of marketed disodium cromoglycate inhalation powder, Intal(R). (C) 1998 Elsevier Science B.V. All rights reserved.