AEROSOL ELECTROSTATICS .1. PROPERTIES OF FINE POWDERS BEFORE AND AFTER AEROSOLIZATION BY DRY POWDER INHALERS

Purpose. To evaluate the dependence of fine particle dose charge (EPD charge) generated from powder inhalers on physico-chemical properties of the inhalation powder, inhaler type, deaggregation mechanism, dose number and/or retained powder. Methods. Electrostatic charges were det ermined on micronized powders and aerosolized fine particle doses with drawn from two, high efficiency, multidose powder inhalers, Turbohaler (TM) and prototype Dryhaler(TM). The behavior of terbutaline sulfate, budesonide, albuterol (sulfate and base), beclomethasone dipropionate and lactose was assessed before and after aerosolization. Results. Bot h inhalers conferred triboelectric FPD charges during aerosolization i n the range -400 pC through +200 pC. Specific charges (charge/unit mas s) on the fine particle doses of budesonide from Dryhaler were signifi cantly less than those from Turbohaler (p < 0.01), Electrostatic charg es on the potentially respirable cloud of terbutaline sulfate generate d by Bricanyl Turbohaler were positive and/or negative and unpredictab le. With Pulmicort Turbohaler, FPD charges on budesonide were always p ositive. Dryhaler was used to determine the chemical dependence of fin e particle triboelectrification during the aerosolization of pure mate rials. A triboelectric series was constructed from the Dryhaler result s ranking the powders from positive to negative as budesonide > lactos e > albuterol sulfate > terbutaline sulfate greater than or equal to a lbuterol greater than or equal to beclomethasone dipropionate. Conclus ions. While there was no evidence of FPD charge dependence upon dose n umber with either inhaler, FPD charges were dependent upon the powder under investigation, as well as the construction and deaggregation mec hanism of the inhaler. The specific charge on the fine particle dose o f budesonide from Turbohaler corresponded to approximately 200 electro nic charges per particle, a value which is known to affect both total and regional aerosol deposition in the human lung. Electrostatic charg e effects may be important determinants of aerosol behavior and should not be neglected.