INFLUENCE OF LABETALOL ON COCAINE-INDUCED CORONARY VASOCONSTRICTION IN HUMANS

PURPOSE: Although labetalol is sometimes given to patients with cocaine-associated chest pain, its influence on cocaine-induced coronary vasoconstriction is unknown. PATIENTS AND METHODS: In 15 patients (7 men, 8 women, aged 40 to 79 years) undergoing catheterization for chest pain. heart rate, mean arterial pressure, and coronary arterial area (by computer-assisted quantitative angiography) were measured (1) at baseline, (2) 15 minutes after intranasal cocaine, 2 mg/kg, then (3) 5 minutes after intravenous saline (n = 6) or labetalol, 0.25 mg/kg (n = 9). RESULTS: Of 40 coronary arterial segments analyzed, cocaine induced a 13% +/- 10% (mean +/- standard deviation) decrease in coronary arterial area in 32. Subsequently, no variable changed after saline administration. Although labetalol reduced mean arterial pressure (117 +/ 14 mm Hg after cocaine, 110 +/- 11 mm Hg after labetalol; p <0.05), it induced no change in the coronary arterial area (3.47 +/- 1.37 mm2 after cocaine, 3.37 +/- 1.32 Mm2 after labetalol; p = NS). CONCLUSION: Labetalol reverses the cocaine-induced rise in mean arterial pressure, but does not alleviate cocaine-induced coronary vasoconstriction.