Efficacy of salbutamol via Easyhaler unaffected by low inspiratory flow

The fine particle dose delivered via dry powder inhalers (DPIs) is often affected by the inspiratory flow rate generated during inhalation. This has clinical implications, since the fine particle dose determines the amount of drug reaching the lungs. With Easyhaler DPI the fine particle dose remains relatively constant over the range of inspiratory flow rates from 30-60 l min(-1). The aim of this study was to confirm that clinical efficacy is maintained even at low flow rates by comparing the bronchodilating effect of salbutamol (100 microg) delivered via Easyhaler at a target inspiratory flow of 30 l 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 technique. Twenty-one paediatric and adult asthmatic patients completed the study, which was conducted over 2 study days. The main outcome parameter was forced expiratory volume in 1 sec (FEV1). The patients were trained to generate a low peak inspiratory flow rate (PIFR) of 30 l min(-1), and the actual PIFR through Easyhaler was recorded. The average PIFR through Easyhaler was 28.7 l min(-1). The difference in the maximum value of FEV1 (FEV1max) between the treatments after drug inhalation was 0.01 l. The mean of FEV1max was 2.67 l after pMDI plus spacer compared to 2.69 l after Easyhaler. Improvements in FEV1 were clinically significant. No significant differences between treatments were found. A reasonably low inspiratory flow rate through Easyhaler produces an equivalent improvement in lung function to a correctly used pMDI plus spacer. Hence, Easyhaler can be used with confidence in patients who may have difficulty in generating a high inspiratory flow rate, such as children and the elderly.