LOADING EFFECT ON PARTICLE-SIZE MEASUREMENTS BY INERTIAL SAMPLING OF ALBUTEROL METERED-DOSE INHALERS

Purpose. The purpose of this study is to investigate the albuterol loa ding effect on particle size measurements by studying the effect of th e amount of albuterol delivered, the number of puffs used, and the sam pling techniques used in particle size measurement. Methods. Particle size distribution profiles for different albuterol loadings were evalu ated using an 8-stage cascade impactor and a sensitive HPLC electroche mical assay method. A commercial albuterol MDI (Proventil(R)) and othe r specially prepared albuterol MDIs were used in the study. Results. A s the amount of albuterol was increased, either by increasing the numb er of puffs or the amount delivered per puff, the measured MMAD increa sed. This increase was more prominent in some formulations (Proventil( R)) than others. Further, albuterol particles previously deposited on the valve and/or actuator didn't play a role in the observed multi-puf f/loading effect. Conclusions. The collection of the least amount of a erosol in a cascade impactor provides a better estimate of MMAD, as it minimizes modifications of the collection surfaces.