CARDIAC ARRHYTHMIAS INDUCED BY TOLAZOLINE (PRISCOLINE)

¹ Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, Michigan

The intravenous administration of tolazoline (Priscoline) induced cardiac arrhythmias, particularly ventricular premature contractions and ventricular tachycardia, in a high percentage of dogs anesthetized with cyclopropane, but not in those anesthetized with pentobarbital. Two dogs under cyclopropane anesthesia died of ventricular fibrillation following the administration of tolazoline.

Small doses of tolazoline (2.5 and 5.0 mgm.kgm.) produced arrhythmias of longer duration, and a more prolonged rise in blood pressure than did larger doses (10 and 20 mgm. kgm.).

Arrhythmias were produced predominantly after initial injections of tolazoline and were associated with a rise in blood pressure. Subsequent injections usually produced a fall in blood pressure and no arrhythmias. However, second small injections did produce serious arrhythmias when given concomitantly with mechanical elevation of the blood pressure. Elevation of the blood pressure did not allow repeated large doses to produce arrhythmias.

It is concluded that arrhythmias produced by tolazoline and by sympathomimetic amines are comparable in that they involve both a rise in blood pressure and a direct action on the myocardium, are facilitated by cyclopropane, and can be inhibited by a direct effect of large doses of tolazoline on the myocardium.

A considerable central nervous system stimulation following tolazoline administration was demonstrated in dogs anesthetized with cyclopropane or pentobarbital.