Resistivities of placebo and active Diskus (R) inhalers compared

Objective: Verbal instruction and demonstration of inhalation technique are essential to enhance the effectiveness of inhalation therapy. Placebo devi ces are commonly used to instruct patients. It is not obvious that patients , who inhale with an adequate flow through an empty placebo Diskus((R)) wou ld also be able to do so with active inhalers containing a strip with powde r. The presence of powder may result in a change in resistivity. We compare d the resistivities of a placebo Diskus((R)) being empty; a powder filled D iskus((R)) inhaler and a Diskus((R)) inhaler with an empty blister. Methods : A Diskus((R)) inhaler was placed in a box, which enabled measurement or p ressure drop and How rates. Ten placebo and ten Ventolin((R)) Diskus((R)) i nhalers were measured. Twelve pressure- and flow-profiles were recorded thr ough each device. After each simulated inhalation through a powder filled b lister, a second inhalation was performed through the empty blister. The re sistivity was calculated by pressure-flow equation. Results: The resistivit y of the empty placebo Diskus((R)) inhaler was slightly but significantly h igher than both blister filled inhalers, with or without powder (0.0215 vs. 0.0211 and 0.0211 (kPa)(0.5) min (-1))(-1)) (P < 0.001). Conclusion: Patie nts who are capable of generating sufficient flow through a placebo Diskus( (R)) will surely be capable of generating equivalent flows through a Diskus ((R)) inhaler containing a strip with active drug substance. (C) 2001 Elsev ier Science B.V. All rights reserved.