The bronchodilator terbutaline enhances digitalis-induced arrhythmia.
The hypothesis that beta 2-sympathomimetics augment digitalis-induced arrhythmias and antagonize its positive inotropic action was tested in isolated, electrically driven guinea-pig left atria. Alone, 0.3 mM terbutaline enhanced myocardial force generation but did not induce dysrhythmia. Terbutaline shortened the time to the onset of 3 microM ouabain-induced arrhythmia by approximately 75% from 19.7 +/- 3.2 minutes to 5.7 +/- 1.2 minutes (p less than 0.005). The enhancement of arrhythmias appeared to be the result of triggering ouabain-induced delayed afterdepolarizations (DAD) into overt arrhythmia. The effect of terbutaline was antagonized by blocking cardiac beta-adrenoceptors with propranolol. Terbutaline did not affect the ability of ouabain to increase myocardial contractility.
Zavecz
J H
JH
Department of Pharmacology, Louisiana State University Medical Center, Shreveport 71130-3932.
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced*; D004071:Digitalis Glycosides / Q000008:administration & dosage / Q000633:toxicity*; D004359:Drug Therapy, Combination; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology; D013726:Terbutaline / Q000008:administration & dosage / Q000633:toxicity*
D004071:Digitalis Glycosides; D010042:Ouabain; D013726:Terbutaline