[Pharmacological studies on expectorants (author's transl)].

Perry and Boyd's method described in 1941 appears to be the most suitable for evaluating the efficacy of expectorants. In this method, changes in volume of respiratory tract fluid (RTF) collected by postural drainage from animals breathing air kept at a constant temperature and humidity are used as criteria. We attempted to improve on the method and to establish the optimum experimental conditions for rabbits. Accordingly, an air conditioning apparatus and tracheal cannula were re-designed and basic experimental conditions essential for quantitative collection of RTF were studied. Using this method, the effects of drugs on the volume of respiratory tract fluid (VRTF) were determined. Bromhexine and emetine as expectorants increased VRTF, and the former showed far more remarkable effects. Codeine and dextromethorphan as antitussives, isoproterenol, clorprenaline and C-78 as bronchodilators decreased VTRF. On the other hand, fominoben and eprazinone as antitussives increased VRTF. Our findings with application of this new approach indicate that this method is applicable for evaluating not only the efficacy of expectorants which increase VRTF but also that of other drugs which decrease VRTF.