Protective effect of choline theophyllinate on histamine, acetylcholine, and propranolol-induced airflow obstruction.

The protective effect of choline theophyllinate, 600 mg orally, was studied by examining the effects on inhaled histamine, acetylcholine, and propranolol in 19 asthmatic patients. Only 9 of them showed a propranolol threshold. This bronchodilator significantly increased the threshold values of histamine and acetylcholine, but showed no protective effect on propranolol thresholds. The histamine threshold changed from 2(2.5 +/- (SD)1.2) to 2(3.8 +/- 1.0) mg/ml (p less than 0.001). With acetylcholine an initial value of 2(4.2 +/- 1.4 mg/ml was determined, which changed to 2(5.5 +/- 1.1 mg/ml (p less than 0.01). The propranolol threshold changed from 1.17% +/- 0.40 to 1.36% +/- 0.40 indicating that theophylline has no statistically significant protective effect on propranolol inhalation. The reproducibility of the challenges was assessed in 8 control patients. A placebo did not significantly change the initial airway reactivity to the three agents. The protective effect of choline theophyllinate on histamine and acetylcholine correlated with the initial degree of reactivity on both agents (r = -0.60; p less than 0.01 and r = -0.84; p less than 0.001, respectively), whereas no significant correlation with the degree of bronchodilation was observed. The latter observation indicates that the protective effect of theophylline does not depend on its bronchodilating activity.