Efficacy of salbutamol via Easyhaler (R) unaffected by low inspiratory flow

The fine particle dose delivered via dry powder inhalers (DPIs) is often af fected by the inspiratory flow rate generated during inhalation. This has c linical implications, since the fine particle dose determines the amount of drug reaching the lungs. With Easyhaler(R) DPI the fine particle dose rema ins relatively constant over the range of inspiratory flow rates from 30-60 1 min(-1). The aim of this study was to confirm that clinical efficacy is m aintained even at low flow rates by comparing the bronchodilating effect of salbutamol (100 mug) delivered via Easyhaler(R) at a target inspiratory fl ow of 301 min(-1) with the same dose of salbutamol via pressurised metered- dose inhaler (pMDI) plus spacer. This was a double-blind, randomized, cross-over study with double-dummy tec hnique. Twenty-one paediatric and adult asthmatic patients completed the st udy, which was conducted over 2 study days. The main outcome parameter was forced expiratory volume in 1 sec (FEV1). The patients were trained to gene rate a low peak inspiratory flow rate (PIFR) of 301 min(-1), and the actual PIFR through Easyhaler(R) was recorded. The average PIFR through Easyhaler(R) was 28.71 min(-1). The difference in the maximum value of FEV1 (FEV1max) between the treatments after drug inhal ation was 0.011. The mean of FEV1max was 2.671 after pMDI plus spacer compa red to 2.691 after Easyhaler(R). Improvements in FEV1 were clinically signi ficant. No significant differences between treatments were found. A reasonably low inspiratory flow rate through Easyhaler(R) produces an equ ivalent improvement in lung function to a correctly used pMDI plus spacer. Hence, Easyhaler(R) can be used with confidence in patients who may have di fficulty in generating a high inspiratory flow rate, such as children and t he elderly.