In vitro performance testing of the novel Medspray wet aerosol inhaler based on the principle of Rayleigh break-up.

Purpose: A new inhaler (Medspray) for pulmonary drug delivery based on the principle of Rayleigh break-up has been tested with three different spray nozzles (1.5; 2.0 and 2.5 mum) using aqueous 0.1% (w/w) salbutamol and 0.9% (w/w) sodium chloride solutions.
Materials and Methods: Particle size distributions in the aerosol were measured with the principles of time of flight (APS) and laser diffraction (LDA).
Results: The Medspray inhaler exhibits a highly constant droplet size distribution in the aerosol during dose emission. Droplets on the basis of Rayleigh break-up theory are monodisperse, but due to some coalescence the aerosols from the Medspray inhaler are slightly polydisperse. Mass median aerodynamic diameters at 60 l.min(-1) from APS are 1.42; 1.32 and 1.27 times the theoretical droplet diameters (TD's) and median laser diffraction diameters are 1.29; 1.14 and 1.05 times TD for 1.5; 2.0 and 2.5 mum nozzles (TD: 2.84; 3.78 and 4.73 mum respectively).
Conclusions: The narrow particle size distribution in the aerosol from the Medspray is highly reproducible for the range of flow rates from 30 to 60 l.min(-1). The mass median aerodynamic droplet diameter can be well controlled within the size range from 4 to 6 mum at 60 l.min(-1).