In vitro comparison of three salbutamol-containing multidose dry powder inhalers - Buventol Easyhaler((R)), Inspiryl Turbuhaler((R)) and Ventoline Diskus((R))

Objective: To compare the in vitro drug delivery characteristics of three s albutamol-containing multidose dry powder inhalers, Buventol Easyhaler(R), Inspilyl Turbuhaler(R) and Ventoline Diskus(R). Materials and Methods: Dose accuracy and consistency, fine particle dose (F PD)/fine particle fraction (FPF), and mass median aerodynamic diameter (MMA D) [measured by Multi-Stage Liquid Impinger] were determined for each inhal er at variable airflow rates (30 and 60 L/min) and at 'equivalent' flow rat es (corresponding to a 4kPa pressure drop). Results: Dose accuracy and consistency (expressed as percentage of label cl aim) of Easyhaler(R) (mean 95%, SD <4.5% at 30 to 60 L/min) compared favour ably with that of Turbuhaler(R) (mean 88%, SD 19% at 60 L/min) and Diskus(R ) (mean 93%,, SD 8% at 90 L/min). The FPF at an 'equivalent' flow rate was 21% for Easyhaler(R) 24% for Turbuhaler(R) and 20% for Diskus(R). The FPF o f Turbuhaler(R) was strongly influenced by flow rate(12 to 24% at 30 to 60 L/min), whereas the FPF of Easyhaler(R) (16 to 23% at 30 to 60 L/min) and D iskus(R) (15 to 21% at 30 to 90 L/min) was less variable. MMAD values for E asyhaler(R) and Turbuhaler(R) were stable at flow rates of 30 to 60 L/min, whereas the particle size distribution for Diskus(R) was more dependent on flow rate. Easyhaler(R) had a considerably lower MMAD than Turbuhaler(R) at flow rates of 30 to 60 L/min. Conclusions: This study demonstrated favourable dose delivery and consisten cy with Buventol Easyhaler(R) compared with Inspiryl Turbuhaler(R) and Vent oline Diskus(R). Delivered dose and FPF showed less flow dependency with Ea syhaler(R) and Diskus(R) than with Turbuhaler(R).