Electrocardiographic changes induced by levamisole hydrochloride in the rat

The acute electrocardiographic effects of levamisole hydrochloride (2, 6, 10 and 20 mg/kg) were examined in the anaesthetized rat. Levamisole caused a fall in heart rate which was greatest at 20 mg/kg. The P-R interval was increased and was longest during the first 2 min after administration of the drug. The Q-T interval, corrected for rate (QTc), was little affected but at 20 mg/kg, 2 of the 5 rats presented 58% and 94% increases over the value at equilibration. Widening of the QRS complex did not occur at 2 and 6 mg/kg, but at 10 and 20 mg/kg a marked widening occurred in 1 out of 4 and 3 out of 5 rats, respectively. Cardiac dysrhythmias occurred even at 2 mg/kg. Severe bradycardia from sino-atrial depression or from A-V block, including Mobitz Type II A-V block, as well as ventricular tachycardia and fibrillation were observed.