Verapamil administration for acute termination of supraventricular tachycardia in dogs

Verapamil, a calcium channel-blocking drug, was administered IV at a dosage that ranged from 0.05 to 0.15 mg/kg of body weight to 14 dogs with supraventricular tachycardia. The dosage was titrated, administering 0.05 mg/kg every 5 to 30 minutes following the initial 0.05 mg/kg dose in all but 1 dog. The drug terminated the arrhythmia in 12 dogs and slowed the ventricular rate in 1 dog. One dog was unresponsive to verapamil administration and became transiently hypotensive after the administration of a total dose of 0.15 mg/kg over 5 to 6 minutes. Various arrhythmias occurred after verapamil administration, but none required additional treatment or caused serious sequelae. Verapamil was an effective treatment for acutely converting supraventricular tachycardia to sinus rhythm in these dogs. It appears to be safe when administered in the aforementioned dosage range.