A COMPARISON OF IN-VITRO DRUG-DELIVERY FROM 2 DRY POWDER INHALERS, THE AEROHALER(R) AND THE ROTAHALER(R)

The particle size distributions of salbutamol and beclomethasone dipro pionate from two unit dose powder inhalers, the Rotahaler(R) and the A erohaler(R), have been assessed. At a flow rate of 60 l/min, mean resp irable fractions by a high precision multi-stage liquid impinger (part icles < 6.8 mum) were : Rotahaler(R), 6.8 and 5.4%, Aerohaler(R), 14.7 and 11.2%, for salbutamol and beclomethasone dipropionate respectivel y. For both inhalers, a large proportion of the dose was retained in t he capsule. The effect of flow rate upon the performance of the Aeroha ler(R) was also investigated. Particle size distributions of salbutamo l and beclomethasone dipropionate from the Aerohaler(R) were assessed by Andersen sampler, at a flow rate of 30 l/min. Reducing the flow rat e was found to reduce the respirable fraction (particles < 5.8 mum, sa lbutamol 9.2%, beclomethasone dipropionate 7.9%). There was considerab le variability in respirable fraction both between replicate measureme nts and between individual inhalers.