Effect of oxitropium bromide (Ba253) on increased airway resistance induced by various agonists and antigen in the guinea pig.

Effects of oxitropium bromide (Ba253), which was administered by inhalation, on the resting and stimulus-induced airway resistance were examined in the artificially ventilated guinea pig and compared with those of ipratropium bromide (Sch1000), atropine and isoproterenol. Results obtained were as follows: 1) Ba253 as well as other reference compounds hardly affected the resting resistance. 2) Ba253 strongly and persistently inhibited the acetylcholine (ACh)-induced resistance. Sch1000 caused a similar but relatively weaker inhibition than Ba253. Either atropine or isoproterenol caused only a transient inhibition. 3) The increase in resistance induced by histamine, serotonin, leukotriene D4 or antigen was prevented by Ba253. Atropine, Sch1000 and isoproterenol also inhibited these reactions, but the effects and the duration were generally weaker and shorter than those of Ba253. 4) Repeated inhalations of Ba253 for 7 days did not influence the inhibition of the ACh-induced increase in airway resistance by this drug. However, isoproterenol tended to attenuate the suppression of the resistance by the drug. From these results, it is suggested that Ba253 is a useful inhalant drug for asthma.