Comparative measurements of pressurised metered dose inhaler (pMDI) stem displacement

A technique was developed to enable direct measurement of a pressurised metered dose inhaler actuation cycle. Three commercially available 250 microg.dose(-1) beclomethasone diproprianate formulations were chosen for analysis; Becloforte (Glaxosmithkline, Sussex), Clenil Forte (Chiesi, Parma, Italy), and BDP-Modulite (Chiesi-Glaxosmithkline). The compression cycle of each device was analyzed and the point of drug actuation (force at which drug was released as an aerosol) was determined. Quantitative analysis of three devices from each product suggested no significant variation in inter-batch actuation force (ANOVA, p < 0.05) (N = 3). Interestingly, a significant variation between product type actuation force was observed (ANOVA, p < 0.05) (N = 3). Actuation forces ranged from 22.33 N +/- 1.44 N for Becloforte to 31.12 N +/- 2.73 N for Clenilforte. In general, such observations suggested a maximum difference of 8.7 N between the two extremes, equivalent to a 39% increase in force required to receive a dose.