Comparison of the speed of bronchodilator action after inhaled fenoterol and rimiterol in reversible airways obstruction

Summary A placebo-controlled study was carried out in 10 patients with reversible airways obstruction to evaluate the speed of action, peak and duration of bronchodilator effect, and effect on heart rate of rimiterol hydrobromide compared with the effects of fenoterol hydrobromide. Both drugs were administered, on successive days, in a dose of 400 μg by inhalation from pressurized aerosols, as was placebo (propellant only). A pressure-volume technique was used which permits repeated measurements of airway resistance with minimum fatigue for the patient. The study clearly demonstrated the difficulties of comparing two bronchodilator aerosols in patients with reversible airways obstruction. Although the differences in airway resistance after placebo inhalation were not significant in themselves, the changes did influence the statistical significance of the changes seen after the active drugs. The results, nevertheless, indicated that both rimiterol and fenoterol produced a comparable and rapid broncho-dilatation, with a significantly better effect on FEV, after rimiterol 3 minutes after inhalation. Fenoterol inhalation was more effective 120 minutes after inhalation. Rimiterol showed no effect on the heart rate compared with a statistically significant increase produced by fenoterol over the first 10 minutes. It is suggested that, in cases where rapid and somewhat shorter duration of bronchodilator effect are required, such as in the acute asthma attack and before sodium cromoglycate, steroid aerosols or exercise, the characteristics of rimiterol would seem to be of value.