The Effects of H1 and H2 Antihistamines on Histamine Inhalation Challenges in Asthmatic Patients1, 2

This study was designed to examine the effect of an H1 antihistamine, chlorpheniramine, an H2 antihistamine, cimetidine, and the combination of chlorpheniramine and cimetidine on histamine-induced bronchoconstriction in a double-blind, randomized protocol on 11 patients with asthma. Each patient underwent a histamine inhalation challenge on 5 separate days. After a control day, histamine inhalation challenges were performed 2 h after the administration of a single oral dose of 8 mg of chlorpheniramine, 300 mg of cimetidine, the combination of chlorpheniramine and cimetidine, or placebo. Baseline pulmonary function measurements were not significantly altered by the 4 treatments. Body plethysmography data and measurements from the forced vital capacity maneuver were obtained before and after the histamine inhalation challenges. The provocation dose of histamine that produced a 20% decrease in forced expiratory volume in one second, a 35% decrease in mean forced expiratory flow during the middle half of the ...