Protective effect of oral oxyphenonium bromide, terbutaline and theophylline against the bronchial obstructive effects of inhaled histamine, acetylcholine and propranolol

The protective effects of oxyphenonium bromide, terbutaline and theophylline were compared in 8 asthmatic patients by determination of the degree of non-specific airway reactivity after 1 week of oral treatment according to a fixed dose scheme in a double-blind random order: oxyphenonium bromide 3 X 10 mg; terbutaline 3 X 5 mg; theophylline 2 X 300 mg and placebo. Controlled, standardized inhalation provocation tests were carried out with histamine, acetylcholine and propranolol. The study was monitored by measuring blood concentrations of the 3 drugs, and their effect on the plasma cAMP concentration was also determined. Significant protection by oxyphenonium bromide against the bronchial obstructive effects of acetylcholine and propranolol was observed, but not against the effect of inhaled histamine. The other two drugs provided no significant protection against the inhaled agents. The absence of any protective effect of terbutaline and theophylline might have resulted from too low a blood concentration. The observed differences in protection could not be explained by changes in pulmonary function. The study suggests dissociation between the bronchodilating effect of a drug and its protective effect against inhaled substances.