Cardiovascular and respiratory effects of antiarrhythmic drugs on conscious beagles.

Cardiovascular effects of antiarrhythmic drugs and their effects on the respiratory rate were examined in conscious beagles. Disopyramide, 1.5 mg/kg i.v., increased the blood pressure and decreased the heart rate, but higher dose of 5 mg/kg i.v. increased both. Disopyramide showed no central nervous side effects. Procainamide, 20 and 60 mg/kg i.v., increased the blood pressure and heart rate without changing the respiratory rate. A higher dose (60 mg/kg i.v.) of procainamide induced vomiting. Lidocaine, 2 and 6 mg/kg i.v., and phenytoin, 3 and 10 mg/kg i.v., simultaneously increased the blood pressure, heart rate and respiratory rate accompanied by excitement, and with a higher dose (6 mg/kg i.v.) of lidocaine, by convulsions. Verapamil, 0.1 and 0.3 mg/kg i.v., induced tachycardia without serious neurological effects. In conscious healthy dogs cardiovascular depressant actions of antiarrhythmic drugs could only rarely be observed.