FRUSEMIDE ANTAGONISES EXERCISE-INDUCED BUT NOT HISTAMINE-INDUCED BRONCHOSPASM

Frusemide has recently been shown to antagonise exercise-induced bronchospasm, an action attributed to blockade of chloride channels in the bronchial epithelium. In order to test the hypothesis that frusemide non-specifically antagonises bronchospasm, we tested the bronchial reactivity to inhaled histamine in ten subjects aged 22 to 35 years, after nebulising 30 mg of frusemide, and after nebulising the frusemide vehicle (water at pH 9.1). The geometric mean (histamine PD20) after inhalation of the solution was 0.6-mu-mol and after frusemide was 0.45-mu-mol. The mean difference in PD20 between control and frusemide was -0.5-mu-mol (frusemide test more reactive) but this change was not statistically significant. We conclude that nebulised frusemide does not antagonise histamine-induced bronchospasm, and that the ability of frusemide to block exercise-induced bronchospasm may be specific to that stimulus.