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 μm) 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 μm nozzles (TD: 2.84; 3.78 and 4.73 μm 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 μm at 60 l.min(−1).