Background: Tiotropium is a new long-acting anticholinergic bronchodilator, which is recommended as first-line therapy in the management of chronic obstructive pulmonary disease (COPD). It is currently available in the form of a dry powder inhaler worldwide. Some COPD patients find it difficult to generate inspiratory flow rates of up to 40 l/min, which is required for the drug to reach the airways. To overcome this, a new pMDI form has been developed for administration of tiotropium in patients with COPD. The clinical efficacy of this mode of tiotropium delivery has, so far, not been compared with the currently available dry powder inhaler (DPI) devices.
Aims and objectives: To compare the bronchodilator effects of a single dose of 18 mcg of tiotropium administered via a pressurized meter dose inhaler (pMDI) and spacer with the currently available DPI form through Rotahaler.
Study design: A randomized, double-blind, double-dummy, three-period, placebo-controlled, crossover, single-center study was conducted in 19 patients with stable COPD. Single doses of tiotropium (18 mcg) or placebo were administered on three separate study days (4-7 days apart) through a Rotahaler and pMDI with a non-static spacer (Zerostat, Cipla Ltd.). During each study visit forced expiratory volume in 1s (FEV(1)) and forced vital capacity (FVC) were measured over a period of 24 h at 11 different time points (0, 15, 30 min, 1, 2, 3, 4, 6, 8, 12 and 24h), using a bellows spirometer (Vitalograph) 2160, UK) while static parameters like inspiratory capacity (IC), residual volume (RV), intrathoracic gas volume (ITGV) and total lung capacity (TLC) were measured by bodyplethysmography (Jaeger Masterscreen, Germany) at 0 min, 3, 8 and 24 h.
Results: Tiotropium administered through both pMDI (and spacer) and DPI showed significantly better mean FEV(1) and mean FVC differences from baseline, in terms of mean maximum change and area under curve over a period of 24 h (AUC(0-24 h)), as compared to placebo. The mean IC and trough FEV(1) values also improved significantly with tiotropium administered through both the devices as compared to placebo. For all these parameters, there was no difference in the efficacy between pMDI and DPI. There was also no significant difference between the time to onset, time to maximum response and duration of response between tiotropium administered through both the study devices. On the other hand, there was no significant difference in RV, ITGV and TLC by a single dose of tiotopium delivered through either of the devices when compared with placebo over a period of 24 h.
Conclusion: This is the first study to demonstrate that tiotropium administered by pMDI and spacer shows a superior time-dependent bronchodilator response when compared to placebo, and that this therapeutic efficacy is similar to tiotropium administered by DPI. We recommend the use of tiotropium administered through a pMDI and spacer to those COPD patients who prefer to use the pMDI device, and especially in those who cannot generate sufficient inspiratory flows required for dry powder inhaler devices.