The reversal of experimental cardiac arrhythmias by indoramin (Wy 21901)

Abstract

Indoramin was approximately equipotent with (±)-propranolol but more potent than lignocaine in reversing adrenaline-induced multiple ventricular ectopic beats and ventricular tachycardia in halothane-anaesthetized cats. Indoramin was more potent than either propranolol or lignocaine in reversing ouabain-induced ventricular tachycardia or fibrillation to sinus rhythm. The local anaesthetic activity of indoramin was three times greater than that of procaine and lignocaine and twice that of (±)-propranol and quinidine when assessed by the guinea-pig wealtest. Experiments on the guinea-pig isolated ileum supporting a local anaesthetic action of indoramin showed that nicotine contractions were reduced by indoramin whereas acetylcholine responses were unaffected. Based on the evidence presented and that published elsewhere, it is considered likely that indoramin abolishes adrenaline-induced arrhythmias by a combination of membrane stabilization and blockade of myocardial α-adrenoceptors whereas ouabain arrhythmias may be reversed by membrane stabilization alone.