Cocaine and alcohol interactions in the rat: contribution of cocaine metabolites to the pharmacological effects

J Pharm Sci. 1999 Apr;88(4):468-76. doi: 10.1021/js980283h.


The pharmacokinetics and pharmacodynamics of cocaine and its three metabolites, benzoylecgonine, norcocaine, and cocaethylene, were investigated in awake, freely moving rats. This work was performed to examine the effect of alcohol coadministration on the metabolic profile of cocaine and to determine the contribution of cocaine metabolites to the pharmacological responses observed after cocaine administration. The plasma and brain extracellular fluid concentration-time profiles were characterized after intravenous (iv) administration of cocaine and the three metabolites in a crossover experimental design. The neurochemical response, measured as the change in dopamine concentration in the nucleus accumbens, and the cardiovascular responses, measured as the change in the mean arterial blood pressure, heart rate, and QRS interval, were monitored simultaneously. Cocaethylene had the highest brain-to-plasma distribution ratio, followed by cocaine, norcocaine, and benzoylecgonine. The estimated total body clearances for cocaine, benzoylecgonine, norcocaine, and cocaethylene were 140 +/- 19, 14.7 +/- 1.2, 130 +/- 19, and 111 +/- 16 mL/min/kg, respectively. Alcohol coadministration increased the formation of norcocaine, decreased the formation of benzoylecgonine, and resulted in the formation of the pharmacologically active metabolite cocaethylene. When cocaine was administered with alcohol, 12.9 +/- 3.1% to 15.3 +/- 2.9% of the cocaine dose was converted to cocaethylene. Benzoylecgonine did not have any central nervous system or cardiovascular activities after iv administration. Compared with cocaine, norcocaine and cocaethylene had more potent and prolonged effects on the neurochemical, heart rate, and QRS interval responses, and were equipotent in increasing the mean arterial blood pressure. These results indicate that changes in the cocaine metabolic profile and the formation of the pharmacologically active metabolite cocaethylene are, at least partially, responsible for the more intense and longer lasting effects reported after using this drug in combination with alcohol.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Algorithms
  • Animals
  • Area Under Curve
  • Biotransformation
  • Blood Pressure / drug effects
  • Brain Chemistry / drug effects
  • Central Nervous System Depressants / blood
  • Central Nervous System Depressants / pharmacology*
  • Cocaine / analogs & derivatives*
  • Cocaine / pharmacokinetics*
  • Cocaine / pharmacology*
  • Dopamine Uptake Inhibitors / pharmacokinetics*
  • Dopamine Uptake Inhibitors / pharmacology*
  • Drug Interactions
  • Ethanol / blood
  • Ethanol / pharmacology*
  • Heart Rate / drug effects
  • Injections, Intravenous
  • Male
  • Rats
  • Rats, Wistar


  • Central Nervous System Depressants
  • Dopamine Uptake Inhibitors
  • Ethanol
  • norcocaine
  • benzoylecgonine
  • cocaethylene
  • Cocaine