Effect of relative humidity on the electrostatic charge properties of dry powder inhaler aerosols.
OBJECTIVE
At present, there is no published data examining the effect of relative humidity on the electrostatic charges of dry powder inhaler aerosols. The charging behaviour of two commercial products, Pulmicort and Bricanyl Turbuhalers, were investigated using an electrical low pressure impactor (ELPI).


METHODS
ELPI was successfully modified to disperse the aerosols at 60 l/min. Four doses from each new inhaler were sampled at 15, 40, 65, and 90% RH. Particles deposited on the impactor stages according to their aerodynamic diameters and their charges were measured simultaneously by the electrometers. The drug in each size fraction was quantified using HPLC.


RESULTS
Both products generated bipolar charges. The charging behaviour of the two types of inhaler showed different humidity dependence although the mass output was not significantly affected. The absolute specific charge of budesonide fine particles from Pulmicort was the lowest at 40% RH but increased at lower and higher RHs. In contrast, the terbutaline sulfate fine particles from Bricanyl followed the expected trend of charge reduction with increasing RH.


CONCLUSIONS
The distinct trends of charging of aerosols from Pulmicort and Bricanyl Turbuhalers was explained by differences in hygroscopicity and other physicochemical factors between the two drugs.
Kwok
Philip Chi Lip
PC
University of Sydney, Building A15, Sydney, NSW 2006, Australia.
Chan
Hak-Kim
HK
D000336:Aerosols; D006813:Humidity; D009330:Nebulizers and Vaporizers; D011208:Powders / Q000737:chemistry*; D055672:Static Electricity
D000336:Aerosols; D011208:Powders