Delivery Characteristics of Albuterol Powder Aerosol by Rotahaler

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Abstract
Delivery characteristics of Rotahaler (200 μg capsule of dry powder) were evaluated for a wide range of inspiratory flow rate. Specific drug doses discharged from Rotahaler and the doses subsequently delivered via an oropharyngeal model were determined by filter sampling and HPLC as a function of inspiratory flow rate. Size distribution of the aerosol was measured at the exit of the oropharyngeal model with a 7-stage cascade impactor. The impactor data were analyzed by both gravimetric and UV spectrophotometric methods. The results show that drug dose (mean ± SD) discharged from the Rotahaler varied widely from 39 ± 32 to 146 ± 11 μg in the inspiratory flow range of 30-120 l/min. Of the dose discharged about 24-34% was lost in the oropharyngeal space in the flow range tested. The drug dose delivered via the oropharyngeal model was between 28 ± 18 and 110 ± 9 μg in the flow range tested: this value represented 15-58% of the unit capsule dose. The delivery dose was consistent only with inspiratory flow rates > 60 l/min. These results and a comparison with a pressurized metered-dose inhaler, Ventolin, are discussed.