Ethanol effects on self-administration of alfentanil, cocaine, and nomifensine in rhesus monkeys

A common form of polydrug use is that of cocaine and ethanol. The identification of an ethanol-cocaine combination product, cocaethylene, with properties in common with cocaine, has led to speculation that this metabolite may contribute to the co-abuse of cocaine and ethanol. In order to determine whether ethanol pretreatments selectively altered cocaine's reinforcing potency, ethanol pretreatments were given to monkeys trained to press levers and receive IV infusions of several doses of cocaine or alfentanil. In addition, nomifensine, a drug which has a mechanism of action similar to cocaine's, was evaluated in the presence and absence of ethanol in monkeys with the cocaine baseline history. Ethanol, in doses ranging from 100 to 1780 mg/kg, given 10 min before the 130-min session, had no effect on responding maintained by alfentanil. These doses also had no significant effect on cocaine-maintained responding, although the potency of cocaine as a reinforcer was increased following administration of 1000 mg/kg ethanol in two of the four subjects. The potency of nomifensine as a reinforcer was significantly increased by 1000 mg/kg ethanol, but again, this enhancement was limited to the same two subjects. These data indicate that, in this paradigm, cocaethylene did not selectively modify cocaine's reinforcing potency, but there appear to be individual differences with respect to ethanol's ability to stimulate rates of drug-maintained responding.