Effects of the antiallergic drug ketotifen on bronchial resistance and beta-adrenoceptor density of lymphocytes in children with exercise-induced asthma.

In a parallel, double-blind, placebo-controlled study we investigated the effect of the antiallergic drug Ketotifen on bronchial resistance (determined body plethysmographically) and beta 2-adrenoceptor density of lymphocytes (determined by 125-iodo-cyano-pindolol binding) in asthmatic children suffering from exercise-induced asthma (EIA). In order to provoke EIA a test which involved running for 7 min was performed with 22 asthmatic children. 13 age-matched children not suffering from asthma served as controls. Control children showed a 30% increase in the number but not in the affinity of beta-adrenoceptors in response to a 7-min run. Asthmatic children with EIA showed no difference in the number and affinity of beta-adrenoceptors under resting conditions when compared with the controls. In contrast to what has been observed with control children, however, no increase in the number of beta-adrenoceptors in response to exercise was observed. A 1-week treatment with placebo neither affected the bronchoconstriction nor the number of lymphocyte beta 2-adrenoceptors. Ketotifen (2 X 1 mg/day for 1 week) protected asthmatic children from EIA, at least in part, and restored the up-regulation of beta-adrenoceptors in response to exercise in 9 of 14 children with EIA. However, no correlation between the serum concentration of Ketotifen and the number of binding sites could be found. It is therefore concluded that the preventive effect of Ketotifen in EIA might also involve mechanisms other than a recovery of the beta-adrenergic system.