In vitro Comparison of Three Salbutamol-Containing Multidose Dry Powder Inhalers

Abstract

Objective: To compare the in vitro drug delivery characteristics of three salbutamol-containing multidose dry powder inhalers, Buventol Easyhaler®, Inspiryl Turbuhaler® and Ventoline Diskus®. Materials and Methods: Dose accuracy and consistency, fine particle dose (FPD)/fine particle fraction (FPF), and mass median aerodynamic diameter (MMAD) [measured by Multi-Stage Liquid Impinger] were determined for each inhaler at variable airflow rates (30 and 60 L/min) and at ‘equivalent’ flow rates (corresponding to a 4kPa pressure drop). Results: Dose accuracy and consistency (expressed as percentage of label claim) of Easyhaler® (mean 95%, SD <4.5% at 30 to 60 L/min) compared favourably with that of Turbuhaler® (mean 88%, SD 19% at 60 L/min) and Diskus® (mean 93%, SD 8% at 90 L/min). The FPF at an ‘equivalent’ flow rate was 21% for Easyhaler®, 24% for Turbuhaler® and 20% for Diskus®. The FPF of Turbuhaler® was strongly influenced by flow rate (12 to 24% at 30 to 60 L/min), whereas the FPF of Easyhaler® (16 to 23% at 30 to 60 L/min) and Diskus® (15 to 21% at 30 to 90 L/min) was less variable. MMAD values for Easyhaler® and Turbuhaler® were stable at flow rates of 30 to 60 L/min, whereas the particle size distribution for Diskus® was more dependent on flow rate. Easyhaler® had a considerably lower MMAD than Turbuhaler® at flow rates of 30 to 60 L/min. Conclusions: This study demonstrated favourable dose delivery and consistency with Buventol Easyhaler® compared with Inspiryl Turbuhaler® and Ventoline Diskus®. Delivered dose and FPF showed less flow dependency with Easyhaler® and Diskus® than with Turbuhaler®.