Cimetidine and cardiac arrhythmia

ABSTRACT

The effects of oral and intravenous [IV] Cimetidine on both the normal ECG and ouabain-induced arrhythmias were investigated in pentobarbital anaesthetized dogs, in order to elucidate its pro or antiarrhythmic potentials. Cimetidine [25 mg/kg] orally for 10 consecutive days or [5 mg/kg] by slow IV infusion over 30 minutes did not induce significant changes in cardiac rate or rhythm. However a bolus injection of 5 mg/kg induced a statistically significant reduction in heart rate by 19% [2 P< .001]. Moreover, Cimetidine by slow IV infusion suppressed ouabain-induced cardiotoxicity as manifested by an increase in the doses of ouabain required to induce premature ventricular beats [PVB] and ventricular fibrillayion [VF] by 18.5% and 17% respectively [P <.005] .Since Cimetidine may be required in intensive care to guard against gastro-intestinal bleeding in critically ill patients, it is advisable to be given by slow IV infusion over 30 minutes. This will not reduce the risk of bradycardia resulting from bolus injections, but may even protect against cardiac arrhythmias that may develop in these patients, secondary to their poor cardiac conditions, excess intra-cardiac histamine release or that may be induced by arrhythmogenic drugs such as digoxin