title: Interactions of beta-adrenoceptor antagonists and thyroid hormones in the control of heart rate in the dog.
abstract: Propranolol, sotalol and nadolol have been infused into conscious dogs, and doses at which the three drugs are equipotent as beta-adrenoceptor antagonists determined. In euthyroid dogs, sotalol was more effective at lowering heart-rate than an equivalent dose of propranolol, while an equivalent dose of nadolol was without effect. Hyperthyroidism potentiated the lowering of heart-rate by sotalol, but inhibited that by propranolol. The effect of sotalol on heart-rate was correlated with its prolongation of the Q-T interval of the ECG. That of propranolol was correlated with its prolongation of the P-R interval. Nadolol did not affect P-R interval or Q-T interval except at relatively high dosage. We conclude that the tachycardia of hyperthyroidism is not affected by blockade of beta-adrenoceptors and therefore that it is not mediated by adrenergic mechanisms. The effectiveness of propranolol and sotalol in lowering heart-rate must be due to actions peculiar to those drugs, and not to beta-adrenoceptor antagonism.
authors.forename: M C
authors.initials: MC
authors.lastname: Allely
authors.forename: A
authors.initials: A
authors.lastname: Ungar
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002231:Carbimazole / Q000494:pharmacology; D004285:Dogs; D004347:Drug Interactions; D004562:Electrocardiography; D006329:Heart Conduction System / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009248:Nadolol; D011412:Propanolamines / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D013015:Sotalol / Q000494:pharmacology; D013963:Thyroid Hormones / Q000494:pharmacology*; D014284:Triiodothyronine / Q000494:pharmacology
chemical_list: D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D013963:Thyroid Hormones; D014284:Triiodothyronine; D009248:Nadolol; D002231:Carbimazole; D011433:Propranolol; D013015:Sotalol; D007545:Isoproterenol