Comparative study of the bronchodilating effects of (-)- and (+)-oxyphenonium bromide.

1. Racemic oxyphenonium bromide, its enantiomers and placebo were inhaled by eight adult patients with chronic airflow obstruction, in a four-way double-blind cross-over study. 2. Forced expiratory volume in one second (FEV1) and slow inspiratory vital capacity (VC) were measured during the first 6 h after inhalation. 3. (+)-Oxyphenonium was found to be the active enantiomer (eutomer), providing better bronchodilation than (+/-)-oxyphenonium. 4. The distomer, (-)-oxyphenonium, showed only a slight effect on FEV1 and VC as compared with placebo.