title: Arrhythmogenic dose of acetylstrophanthidin unchanged by beta-sympathomimetics in conscious dogs.
abstract: The enhanced arrhythmogenic risk of combined treatment with cardiac glycosides and beta-sympathomimetics is referred in some textbooks, but only a few detailed studies on in vivo models are available. We therefore investigated this problem in conscious dogs in an intraindividual study. We determined the dose of acetylstrophanthidin (intravenous infusion of 5 mcg/kg per min), which provoked ventricular premature beats with and without concomitant treatment with the partial beta-agonistic compounds doxaminol (3 mg/kg p.o.), prenalterol (0.4 or 1.0 mg/kg p.o.) or isoprenaline (0.31 +/- 0.100 mcg/kg per min). In some dogs a coronary artery was narrowed in order to reduce the coronary blood supply. The arrhythmogenic dose of acetylstrophanthidin was nearly the same in all the groups investigated (range from 52.1 +/- 5.66 to 59.9 +/- 3.23 mcg/kg). Whereas the arrhythmogenic dose of acetylstrophanthidin was unchanged by beta-sympathomimetics, the combination of the glycoside and each of the beta-agonistic drugs increased the contractile force more than did either single compound. We therefore conclude that the arrhythmogenic risk of the combination of glycosides and beta-sympathomimetics may be--at least in experimental models--less than has been suggested in the past.
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced*; D003327:Coronary Disease / Q000188:drug therapy; D003990:Dibenzoxepins / Q000494:pharmacology; D004285:Dogs; D004361:Drug Tolerance; D005260:Female; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D011217:Practolol / Q000031:analogs & derivatives / Q000494:pharmacology; D011294:Prenalterol; D013327:Strophanthidin / Q000031:analogs & derivatives* / Q000633:toxicity
chemical_list: D000318:Adrenergic beta-Agonists; D003990:Dibenzoxepins; C034187:doxaminol; D013327:Strophanthidin; C004681:acetylstrophanthidin; D007545:Isoproterenol; D011294:Prenalterol; D011217:Practolol