Verapamil inhibits ethanol elimination and prolongs the perception of intoxication

Ten young healthy men received verapamil (80 mg every 8 hours for 6 days) or placebo in a blinded, randomized, crossover design. On the sixth day, ethanol was administered as a single oral dose (0.8 gm/kg), and blood samples were collected over the following 12 hours for determination of verapamil, norverapamil, and ethanol concentrations. Compared with placebo, verapamil increased the peak blood ethanol concentration (106.45 ± 21.40 to 124.24 ± 24.74 mg/dl, p < 0.05) and area under the ethanol concentration versus time curve (365.67 ± 93.52 to 475.07 ± 97.24 mg · hr/dl, p < 0.005). Verapamil areas under the concentration versus time curves (AUC) were positively correlated (r = 0.71, p < 0.05) to increased ethanol blood AUC values. Each subject's perception of ethanol intoxication was measured by use of a simple visual analog scale. Compared with placebo, verapamil significantly increased area under the effect versus time curve (10.19 ± 7.6 to 13.83 ± 7.81 cm · hr, p < 0.002) but did not change the peak effect or time to peak effect. Ethanol effect versus concentration plots were not significantly different between verapamil and placebo treatment phases when increased ethanol concentrations during verapamil therapy were taken into account. The findings of our study suggest that verapamil significantly inhibits ethanol elimination, resulting in elevated blood ethanol concentrations that prolong the intoxicating effects of alcohol. Clinical Pharmacology and Therapeutics (1992) 52, 6–10; doi: 10.1038/clpt.1992.96