Antiarrhythmic activity of four pteridine compounds in ouabain intoxication

The antiarrhythmic effects of 4 pteridine analogues, 2 of which are potassium-sparing diuretics, triamterene (2, 4, 7-triamino-6-phenylpteridine) and [2-phenyl-4, 7 diaminopteridine-6-(N-diethylaminoethyl) carboxamide] and 2 of which have no diuretic effects [2-phenyl-4, 7-diaminopteridine-6-(N-2-hydroxyethyl) carboxamide], on ouabain-induced ventricular tachycardia in intact pentobarbital-anesthetized dogs were investigated. Ouabain was given as a continuous infusion 2 mug/kg/min intravenously until 5 min after the onset of a sustained ventricular tachycardia. It was found that both 6-(N-dimethylaminopropyl) and 6-(N-diethylaminoethyl) carboxamide derivates of the pteridine had a significant protective effect against ouabain-induced ventricular tachycardia in dogs that had been pretreated with a dose of 5 mg/kg intravenously. At this dose the 2 pteridine compounds with diuretic activity exhibited a transient antiarrhythmic effect in abolishing the ouabain-induced ventricular tachycardia while those without diuretic properties failed to suppress the ventricular tachycardia.