title: The effect of the combination of quinidine and propranolol upon atrial and ventricular automatically in dogs.
abstract: The effects of quinidine, propranolol and their combination on atrial and ventricular automaticity were studied in pentobarbital-anesthetized dogs with complete heart block produced by injection of 40% formalin. The indices of atrial and ventricular automaticity were the intrinsic rate and the asystole interval, 10-beat period, and beats per 30 seconds after cessation of a 2-minute overdrive. Potentiation was considered to be a response produced by the combination of a half-dose of quinidine plus a half-dose of propranolol significantly greater than that produced by the full dose of either drug. Two combinations were studied: combination I consisted of 1.0 mg/kg of quinidine and 0.04 mg/kg of propranolol while combination II consisted of 2.0 mg/kg of quinidine and 0.08 mg/kg of propranolol. Neither combination potentiated the action of the individual drugs on the ventricle. Both combinations produced a potentiation of the individual drug effects on atrial intrinsic rate, asystole interval, and 10-beat period while only combination II potentiated the individual drug effects on atrial beats per 30 seconds. These studies indicate that the enhanced effect of the quinidine-propranolol combination in conversion of atrial tachyarrhythmias to sinus rhythm may be a function of its potentiation of the ability of the individual drug to depress atrial automaticity.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D004357:Drug Synergism; D005260:Female; D006323:Heart Arrest / Q000503:physiopathology; D006325:Heart Atria / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects*; D006352:Heart Ventricles / Q000187:drug effects; D008297:Male; D011433:Propranolol / Q000494:pharmacology*; D011802:Quinidine / Q000494:pharmacology*
chemical_list: D011433:Propranolol; D011802:Quinidine