Drug effect on bronchial response to PGF2 alpha and water inhalation.

A new method of challenge with H2O is described after summarizing the results of previous studies concerning the pharmacological prevention of bronchoconstriction induced by PGF2 alpha and by ultrasonic mist of distilled water (H2O). This provides a simple, rapid and reproducible way of obtaining linear dose-response curves by plotting times of exposures against absolute or percent increases in sRaw. The preventive activity of several drugs against this type of bronchospasm has been tested. Beta 2-stimulants (fenoterol) were the most effective, both in terms of intensity and duration of action (more than 6 hours). DSCG, tiaramide and nifedipine were also efficient. Oxitropium bromide was almost ineffective, in spite of the comparatively high doses used. The H1 and H2 antihistamines chlorpheniramine and ranitidine were ineffective. The possible implications of these results are discussed, mainly in order to try to understand the mechanism of H2O bronchospasms, for which airways cooling does not seem at work.