Bronchial spasmolytic action of terbutaline and fenoterol compared with that of ipratropium bromide in the anaesthetized dog.
Continuous recordings of heart rate, respiration rate, minute volume and bronchial resistance were made over a period of altogether three hours in spontaneously breathing dogs anaesthetized with chloralose. At hourly intervals, before and 1 and 2 hr after the administration of bronchodilators, bronchial spasm was induced by inhalation of an acetylcholine solution. Two beta2-stimulants, terbutaline and fenoterol, were administered by inhalation in doses of 0.5, 0.16 and 0.05 mg/kg and 0.1, 0.3 and 0.01 mg/kg respectively. For comparison, an atropine derivative, ipratropium bromide, was also given by the same route in doses of 0.04 and 0.01 mg/kg. Controls received normal saline. Terbutaline and fenoterol caused an increase in heart rate, respiration rate and minute volume. Acetylcholine-induced bronchial spasm was inhibited to the extent of 10--70% for 2 hr after the administration of terbutaline, and by 15--70% after fenoterol. The acetylcholine antagonist ipratropium bromide caused only transient changes in heart rate, respiration rate and minute volume. Acetylcholine-induced bronchial spasm was inhibited by 95% and 80% for 2 hr after doses of 0.04 and 0.01 mg/kg, respectively. Fenoterol had a slightly greater central stimulant effect than terbutaline; ipratropium bromide displayed no stimulant activity.
D000109:Acetylcholine / Q000494:pharmacology; D000403:Airway Resistance / Q000187:drug effects; D000758:Anesthesia; D000818:Animals; D001286:Atropine Derivatives / Q000494:pharmacology*; D001986:Bronchial Spasm / Q000139:chemically induced*; D004285:Dogs; D004983:Ethanolamines / Q000494:pharmacology*; D005280:Fenoterol / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects; D009241:Ipratropium / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects; D013726:Terbutaline / Q000494:pharmacology*; D013997:Time Factors
D001286:Atropine Derivatives; D004983:Ethanolamines; D005280:Fenoterol; D009241:Ipratropium; D013726:Terbutaline; D000109:Acetylcholine