Antiarrhythmic evaluation of naloxone against acute coronary occlusion-induced arrhythmias in pigs.

Naloxone pretreatment (1.0, 3.0 and 10.0 mg/kg i.v.) failed to protect anesthetized pigs from cardiac arrhythmias including ventricular fibrillation (VF) and death following acute occlusion (20 min) or reperfusion of the left anterior descending coronary artery. These findings suggest that opiate-like substances possibly released by the ischemic myocardium do not contribute significantly to the etiology of cardiac arrhythmias, or sudden death associated with the early stages of myocardial infarction in pigs. The effectiveness of naloxone in preventing acute ischemia-induced arrhythmias in rats may be due to mechanisms other than opiate-receptor blockade.