Influence of the storage orientation on the aerodynamic particle size of a suspension metered dose inhaler containing propellant HFA-227.

Presented in this work are the results of a study designed to investigate the impact of the storage position on the particle size distribution (PSD) of a steroid suspension metered dose inhaler (MDI) containing propellant HFA-227. It was hypothesized that the orientation of MDI samples upon storage could influence the PSD of the emitted dose, since it determines the amount of contact the liquid formulation has with the valve and therefore the quantity of nonvolatile leachable materials from the valve components that may enter the product and potentially impact the aerosol spray dynamics. Samples stored in the valve down orientation (i.e., complete contact of the liquid formulation with the valve) showed a higher level of leachables compared to those samples stored valve up (i.e., minimal contact of the formulation with the valve). The valve down samples were found to produce larger particles in the emitted aerosol spray using both cascade impaction, the preferred method of regulatory submission, as well as laser diffraction. It was postulated that the larger particle size of the inverted samples was attributed to its higher levels of leachables. Based on our findings, it is recommended that in order to set appropriate controls on the product PSD, the storage orientation of the product will need to be considered.