Long-term modification on histamine-induced bronchoconstriction by disodium cromoglycate and ketotifen versus placebo.

In order to compare long-term changes induced on a wide spectrum of bronchial hyperreactivity (BH) by the antiallergic drugs disodium cromoglycate (DSCG) and ketotifen, 56 asthmatic patients (age range 15-55 years) were studied. Patients were allocated to three groups with similar age and BH level. During 2 months, 15 individuals inhaled 20 mg DSCG four times a day, 14 took ketotifen 1 mg twice a day orally and 14 one placebo (lactose) capsule twice a day. After preliminary results, an additional group of 13 patients took clemastine 1 mg orally twice a day for 1 week. Only the ketotifen and clemastine groups differed significantly from the placebo group on shifting log dose-response curves of inhaled histamine. In addition, no significant difference was seen between the ketotifen and clemastine groups. These results suggest that changes induced by ketotifen were mainly related to its powerful antihistamine action; similarly, nonspecific BH is not wholly dependent on mediator release.