Cocaethylene: a unique cocaine metabolite displays high affinity for the dopamine transporter.

Concurrent cocaine and alcohol use is common practice in the general population, as indicated by recent prevalence studies. In the presence of ethyl alcohol, cocaine is metabolized to its ethyl homolog, cocaethylene. The transesterification of cocaine and ethanol to cocaethylene takes place in the liver and represents a novel metabolic reaction. Cocaethylene was detected in postmortem blood, liver, and neurological tissues in concentrations equal to and sometimes exceeding those of cocaine. In vitro binding studies demonstrate that cocaethylene has a pharmacological profile similar but not identical to that of cocaine at monoamine transport sites assayed in the human brain. Cocaethylene was equipotent to cocaine at inhibiting [3H]mazindol binding to the dopamine transporter. The blockade of dopamine reuptake in the synaptic cleft by cocaethylene may account for the enhanced euphoria associated with combined alcohol and cocaine abuse.