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 dipropionate from two unit dose powder inhalers, the Rotahaler(R) and the Aerohaler(R), have been assessed. At a flow rate of 60 l/min, mean respirable fractions by a high precision multi-stage liquid impinger (particles < 6.8 mum) were : Rotahaler(R), 6.8 and 5.4%, Aerohaler(R), 14.7 and 11.2%, for salbutamol and beclomethasone dipropionate respectively. For both inhalers, a large proportion of the dose was retained in the capsule. The effect of flow rate upon the performance of the Aerohaler(R) was also investigated. Particle size distributions of salbutamol and beclomethasone dipropionate from the Aerohaler(R) were assessed by Andersen sampler, at a flow rate of 30 l/min. Reducing the flow rate was found to reduce the respirable fraction (particles < 5.8 mum, salbutamol 9.2%, beclomethasone dipropionate 7.9%). There was considerable variability in respirable fraction both between replicate measurements and between individual inhalers.