Drug delivery characteristics of Bricanyl Turbohaler TM dry powder inhalers

Abstract

The Turbohaler TM is the one multidose reservoir type dry powder inhaler (DPI) with significant clinical usage but there is little information on the precision of its single dose delivery characteristics. The single dose delivery efficiency of terbutaline sulphate (nominally 500 μg) from two batches of Bricanyl Turbohalers TM (11 and 59 devices) has therefore been studied at air flow rates of 28–30 and 60 1 min −1 which are clinically relevant test conditions for this DPI. At 60 1 min −1 statistically significant differences both within and between batches were obtained for emitted dose (± SD, n = 110, 130), 421 ± 73, 387 ± 58μg and fine particle dose (0.5–6.4 μm MMAD), 249 ± 41, 214 ± 44μg. These data imply an emitted dose range of ± 50% and a fine particle dose range of ± 70% from this DPI system. Through-life total dose emission in terms of the average values remain consistent. Reducing air flow rates to approx. 30 1 min −1 lowered the mean emitted dose by about one third with the clinically important fine particle dose being reduced 3-fold to 59 ± 25 μg; this underlines the likely sensitivity of effective delivery, to patients' lung function. These results reinforce the need to provide single dose data at clinically relevant flow rates in the assessment of DPI performance. Expressing data as mean performance for a cumulative series of dose units smooths down this single dose variability by a factor of two.