Bronchodilating and density dependence effects of fenoterol, ipratropium bromide and Duovent in reversible chronic obstructive pulmonary disease.

The bronchodilating effect of Duovent (0.2 mg fenoterol +0.8 mg ipratropium bromide) was compared with that of each of its components at the same doses. Twenty patients were included in the trial. Maximum expiratory flow-volume curves with air and helium-oxygen, intrathoracic gas volume and airway conductance were used for assessing the bronchomotor tone before and 15, 30, 60, 240 and 360 min after drug administration. All the drugs showed a significant bronchodilating effect. No differences between Duovent and fenoterol or ipratropium bromide were observed except a slight but statistically significant greater decrease of ITGV with Duovent. When expressing the data as percentage variation of the initial values, Duovent induced a better effect than the other drugs. The evaluation of density dependence was highly disappointing, and no conclusion can be drawn.