Oxatomide is a potent inhibitor of both the release and effects of allergic mediators and is similar to calcium antagonists in chemical structure. It prevents histamine release by inhibiting not only the increase in calcium intake, but also intracellular calcium release. We investigated its effect on methacholine-induced and exercise-induced bronchoconstriction in asthmatic children. Methacholine challenges were performed after oral administration of 0.88 mg/kg oxatomide or placebo in nine asthmatic children in a double-blind placebo-controlled study. Respiratory thresholds were improved in seven patients and log PC20 in the oxatomide group (6.65 +/- 1.34 micrograms/mL) was significantly higher than that in the placebo group (5.74 +/- 1.04 micrograms/mL) (P < .05). Exercise challenges were performed after oral administration of 1.5 mg/kg oxatomide or placebo in eight asthmatic children in a double-blind placebo-controlled study. Oxatomide produced acute bronchodilatation with 6.1% improvement on an average in FEV1. The mean maximal % fall obtained by oxatomide was 13.5%, while that by placebo was 22% (P < .05). These results indicate that oxatomide reduces nonspecific bronchial hyperresponsiveness.