title: Nature of the inhibition by amiodarone of isoproterenol-induced tachycardia in the dog.
abstract: Inhibition of in vivo isoproterenol-induced tachycardia by i.v. amiodarone was studied in anesthetized dogs. Significant dose-response curves to isoproterenol could not be obtained in single animals because of the time-dependent lowering of the inhibitory effect of the drug. Single isoproterenol injections after amiodarone in 105 dogs allowed dose-response curves to be obtained. The slope of these curves decreased with increasing doses of amiodarone, and the maximal rate stimulation diminished also in a dose-dependent manner. These features are consistent with a non-competitive inhibition pattern. A mechanism of the beta-adrenergic antagonism developed by amiodarone is suggested.
mesh_terms: D000638:Amiodarone / Q000494:pharmacology*; D000818:Animals; D001572:Benzofurans / Q000494:pharmacology*; D004285:Dogs; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D007545:Isoproterenol / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D008297:Male; D013268:Stimulation, Chemical
chemical_list: D001572:Benzofurans; D007545:Isoproterenol; D000638:Amiodarone