Aerodynamic size distribution, hygroscopicity and deposition estimation of beclomethasone dipropionate aerosol.

Aerodynamic size distribution and aerodynamic mass per dose of beclomethasone dipropionate aerosol were measured at 24 and 95% relative humidity. At high humidity, the count median aerodynamic diameter was unchanged, mass median aerodynamic diameter increased from 2.01 micrometer to 2.68 micrometer, particle number/dose from 41.3 x 106 to 78.3 x 106, and aerodynamic mass per dose from 23.7 to 60.0 microgram. The quantity of active ingredient estimated to be in the 23.7 microgram aerodynamic mass at low humidity was 19.7 microgram. From data previously available describing average deposition fraction as a function of aerodynamic diameter, 6.7 microgram or 13% of the total dose of 50 microgram produced by the metered dose canister would be expected to deposit in the lower respiratory tract.