Effects of pretreatment with monensin (150 ug/kg), atenolol (0.3 mg/kg), atenolol plus monensin, verapamil (0.38 mg/kg), verapamil plus monensin, glibenclamide(0.38 mg/kg) and glibenclamide plus monensin on the dose of digoxin required to induce premature ventricular contractions (PVCS) in anaesthetized guinea-pigs were studied. Monensin reduced while atenolol increased the dose of digoxin required to produce PVCS. Atenolol plus monensin increased the dose of digoxin required to produce PVCS in presence of monensin alone. Verapamil reduces the arrhythmogenic effect of monensin on digoxin. Glibenclamide antagonises the effect of monensin on digoxin induced PVCS.
From the present data it could be concluded that, monensin enhances digoxin-induced arrhythmias in guinea-pigs. The enhancement of arrhythmias in presence of monensin may be due to catecholamine release by monensin and or may be due to the decrease of action potential duration which in part result from opening of ATP dependent K+ channels in guinea pig ventricular muscle these channels, which blocked by glibenclamide.