The efficacy of a low-dose, monodisperse parasympathicolytic aerosol compared with a standard aerosol from a metered-dose inhaler

Objective: In previous experiments we showed that monodisperse bronchodilator aerosols with a median mass aerodynamic diameter of 2.8 mu m induced stronger bronchodilatations than larger aerosols and that the dilatations were clinically relevant at low doses. To discover whether the bronchodilator effects of these low-dose monodisperse aerosols differed from those of standard dosages delivered by metered-dose inhalers, we carried out a comparative trial. Methods: Ten stable outpatients with a mean forced expiratory volume in 1 s (FEV1) of 58.1% of the predicted value inhaled a placebo aerosol, 8 mu g of a 2.8-mu m monodisperse ipratropium bromide aerosol and 40 mu g from a metered-dose inhaler plus spacer; lung-function measurements followed. Data were analysed with repeated measurements analysis of variance (ANOVA). Results: Greater improvements than with placebo were evident for the forced vital capacity (FVC), the FEV1, the specific airway conductance (sGaw), the peak flow (PEF) and the maximum expiratory flow at 75% of the forced vital capacity (MEF75). In these cases, the low-dose 2.8-mu m aerosol proved to be equivalent to the higher-dose metered-dose inhaler. Conclusion: By changing the polydisperse characteristic of inhaled aerosols to a monodisperse pattern, the dose of the drug administered can be reduced without loss of efficacy.