AN ASSESSMENT OF THE API AEROSIZER(R) FOR THE REAL-TIME MEASUREMENT OF MEDICAL AEROSOLS FROM PRESSURIZED METERED-DOSE INHALER (PMDI) SYSTEMS

The Aerosizer(R) is becoming widely used as a rapid method for obtaini ng aerodynamic particle size distributions of aerosols from pMDIs and associated drug delivery devices, as an alternative to more time-consu ming methods such as cascade impactors or liquid impingers. It is typi cally used with purpose-built attachments for sampling the aerosol in a simulated inhalation (AeroBreather(R)), and subsequently diluting th e sample to the point at which individual particles are separately mea sured (AeroDiluter(R)). It is possible to obtain an indication of aero sol mass concentration (mass loading), although such data do not neces sarily equate to active drug concentration because the technique does not involve a specific chemical assay. Data are presented that indicat e that the performance of the Aerosizer(R) system may be more drug-spe cific than had previously been thought. In particular, certain pMDIs a ppear to create such highly concentrated aerosols that meaningful inte rpretation of mass loading data may not be possible, even with maximum aerosol dilution. The influence of photomultiplier detector voltage o n measured size distributions also varies with drug type. While the Ae rosizer(R) is a valuable tool for rapid comparative work, there is sti ll a need to compare data with more traditional methods where drug ass ay is performed in order to be sure that the instrument is set up corr ectly for the drug being examined. (C) 1996 American Association for A erosol Research.