Coronary vasodilation caused by intravenous cocaine in the anesthetized beagle

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Abstract
The aim of this study was to determine the effect of intravenous cocaine on the coronary circulation in the dog. Sixteen beagles separated into three groups were administered either cocaine (n = 8) or lidocaine (n = 4) at doses of 0.4, 2.0, and 10.0 mg/kg under conditions of constant coronary blood flow. A third group of beagles (n = 4) was administered cocaine under conditions of natural coronary blood flow. In the first group, the lowest dose of cocaine had no significant effect on coronary perfusion pressure, even though it increased mean systemic arterial pressure by 10% (p < 0.05). The second two doses decreased coronary perfusion pressure by 13 (p < 0.05) and 68% (p < 0.05), respectively. In the second group, the lowest dose of lidocaine did not significantly affect coronary perfusion pressure. However, the second two doses significantly decreased coronary perfusion pressure by 22 (p < 0.05) and 45% (p < 0.05), respectively. Under conditions of natural coronary blood flow and coronary perfusion pressure, these same doses of cocaine increased coronary blood flow by 25, 63, and 175%, respectively. All coronary vascular responses occurred 60 s after administration of cocaine or lidocaine. We conclude that cocaine causes rapid, dose-dependent coronary vasodilation in the anesthetized beagle. The coronary vasodilation appears to be related to cocaine's known, local anesthetic properties.Key words: constant flow, vasodepressor, lidocaine, local anesthetic, myocardium.