Simulated respiratory system for in vitro evaluation of two inhalation delivery systems using selected steroids.

A simulated respiratory system was developed for the in vitro evaluation of two differently designed oral inhalation delivery systems. The deposition properties of a newly designed delivery system used for triamcinolone acetonide were compared to the more conventional, commercially available adapter utilized for an aerosol containing beclomethasone dipropionate. The simulated respiratory system was constructed so that the delivered dose of active ingredient could be classified into two fractions: the fraction that would be deposited in the oral cavity and throat and the fraction that would reach the desired site of activity in the respiratory tract. Based on this method, the newly designed system delivered more than 95% of the labeled dose to the desired site. The beclomethasone dipropionate aerosol system, which was observed to discharge the active ingredient with a greater intensity, delivered approximately 40% of the labeled dose. The particle-size distribution of the dose dispensed from the newly designed delivery system attached to the triamcinolone acetonide aerosol was determined using an impactor technique. No effort was made to correlate these results with an in vivo response.