BRONCHODILATING ACTIVITY OF AN H-1 BLOCKER, CHLORPHENIRAMINE

[摘要] In 10 subjects with allergic asthma, forced expiratory flows (FEF) were recorded on different days, at comparable baseline values, before and up to 5 h after administration of 8 mg per os (po) chlorpheniramine [CP], 10 mg i.v. CP (repeated twice), 5.5 mg/kg i.v. aminophylline and 30 mg po butabarbital and during a day without drug. Chlorpheniramine administered i.v. produced reproducible increases (+.DELTA.) in FEF, starting at 15 min, peaking at 120 min, and still persisting at 5 h; the peak +.DELTA. averaged 15% for FEV1 [forced expiratory volume in 1s] and 27% to 53% for flows at low lung volume. FEF showed a comparable +.DELTA. after aminophylline, a smaller +.DELTA. after orally administered chlorpheniramine and no significant +.DELTA. during butabarbital or control sessions. The ratio change over time/variability was higher for FEV1, FEF50%, and FEF25%-75% than for the remaining parameters. In 6 subjects a double-blind study (chlorpheniramine vs. saline solution) confirmed the effectiveness of the doses administered in the open study. In 3 subjects, 10 mg i.v. chlorpheniramine was given at 4 different baseline values; the highest +.DELTA. occurred when the basal FEV1 was .apprx. 50% of the predicted value and the basal FEF at low lung volume 30% to 40% of the predicted value. In 2 subjects, log dose-response curves to 2.5, 5.0 and 10.0 mg i.v. chlorpheniramine were obtained by using FEV1, FEF50% and FEF25%-75%. Chlorpheniramine in high i.v. doses can apparently dilate the bronchi, the +.DELTA. FEF depending on the dose, the percent of the predicted basal FEF value, and individual responsiveness. Within the dose range used, bronchodilatation to chlorpheniramine and aminophylline administered i.v. was best detected by FEV1, FEF50% and FEF25%-75%.