Inhalation characteristics and their effects on in vitro drug delivery from dry powder inhalers .2. Effect of peak flow rate (PIFR) and inspiration time on the in vitro drug release from three different types of commercial dry powder inhalers

Abstract

Three commercial dry powder inhalers with completely different dosing and powder disintegration principles were evaluated in an in vitro deposition study. A four-stage cascade impactor was used for the range of flow rates between 20 and 60 1/min. Turbuhaler, Diskhaler and Spinhaler showed increasing amounts of drug discharged from the dose system with increasing peak inspiratory flow rate (PIFR). Only for the Spinhaler, was discharge influenced by total inspiration time as well. All three inhalers also showed improved powder disintegration with increasing PIFR. Highest fine particle yield was obtained from the Turbuhaler, reaching a maximum of 35-40% of the nominal dose at flow rates of 50-60 1/min. In comparison, less than 10% of the nominal dose from the Spinhaler and on average 23% from the Diskhaler were released as fine drug particles at 60 1/min. From the work of inspiration involved, it has been concluded that a short and fast inspiration through the Turbuhaler gives an optimal result from fine particle output and from efficiency point of view