Protective effects of ketotifen on allergen-induced bronchoconstriction and skin weal

A single-blind cross-over method was used to investigate the effects of ketotifen on the total respiratory resistance response curve to inhalation of a high concentration of allergen (1:5 w/v house dust or 1:10 w/v Japanese cedar pollen) and the weal response to intradermal injection of serially diluted allergen (1:10(3)-1:10(6) w/v). Five subjects received 2 mg of ketotifen every 12 hr for the first week and an inactive placebo in the same manner for the second week. The remaining five subjects received the placebo for the first week and ketotifen for the second week. Ketotifen did not alter base-line pulmonary function, but significantly delayed the time from the start of allergen exposure to the beginning of elevation of total respiratory resistance (P less than 0.02), and the time from the start of allergen exposure to the point at which total respiratory conductance decreased by 35% from the base-line value (P less than 0.01). Ketotifen also decreased skin test sensitivity significantly (P less than 0.01).