Naloxone inhibits arrhythmias induced by coronary artery occlusion and reperfusion in anaesthetized dogs.

The intravenous administration of naloxone 2 min before coronary artery occlusion in anaesthetized dogs reduced the incidence and severity of cardiac arrhythmias during coronary occlusion (20 min) and reperfusion (120 min) in a dose-related manner. It also reduced the mortality. At a dose of 1 mg kg-1 (the maximum dose used in this study) naloxone abolished the appearance of the life threatening ventricular fibrillation (VF) and ventricular tachycardia (VT) and as a consequence all dogs in this group survived. The results suggest a possible involvement of endogenous opioid peptides in arrhythmogenesis during coronary occlusion and reperfusion in the dog.