Prevention and reversal of ouabain-induced cardiotoxicity by naloxone in the guinea-pig.

The effects of pre- and post-treatment with naloxone on the cardiotoxicity of ouabain in the guinea-pig were studied. After pretreatment with naloxone, the dose of ouabain required to induce ventricular arrhythmias and cardiac arrest were significantly increased, in a dose-dependent manner, compared with the control, indicating a protective effect of naloxone against digitalis intoxication. Administration of naloxone at the onset of cardiac arrhythmias induced by a lethal dose of ouabain restored the cardiac rhythm and consequently saved life in seven out of eight animals, indicating an antiarrhythmic effect of naloxone in digitalis-intoxicated guinea-pigs. The protective and antiarrhythmic effects of naloxone against digitalis intoxication have clinical implications.