title: Polymyxin B and heart muscle.
abstract: The effects of the polypeptide antibiotic, polymyxin B, on myocardial contractility were studied in t;e isolated rat heart muscle. Five different doses of polymyxin B were tested. There were no changes in contractility with does ranging from the clinical therapeutic value to three times greater. There was an initial increase and then depression with a dose six times greater than the therapeutic dose. There was no direct competitive interaction between polymyxin B and halothane or Ca2+. This suggests that polymyxin B does not depress the myocardium in clinical doses and does not interfere with Ca2+ influx at the myocardial cell membrane.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006221:Halothane / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D011112:Polymyxin B / Q000494:pharmacology*; D011113:Polymyxins / Q000494:pharmacology*; D051381:Rats
chemical_list: D011113:Polymyxins; D011112:Polymyxin B; D002118:Calcium; D006221:Halothane