PT  - JOURNAL ARTICLE
AU  - G. Winger
AU  - C. M. Galuska
AU  - S. R. Hursh
AU  - J. H. Woods
TI  - Relative Reinforcing Effects of Cocaine, Remifentanil, and Their Combination in Rhesus Monkeys
AID  - 10.1124/jpet.105.100461
DP  - 2006 Jul 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 223--229
VI  - 318
IP  - 1
4099  - http://jpet.aspetjournals.org/content/318/1/223.short
4100  - http://jpet.aspetjournals.org/content/318/1/223.full
SO  - J Pharmacol Exp Ther2006 Jul 01; 318
AB  - Human polydrug abusers often take combinations of opioids and stimulants, but it is not clear why. Behavioral economics with demand curve analysis is uniquely able to separate two of the possibilities: that the drug combination increases the reinforcing potency of the component drugs or that the drug combination is a more effective reinforcer than either drug alone. Rhesus monkeys self-administered a range of doses of cocaine, remifentanil, and combinations of the drugs through indwelling intravenous catheters; the number of responses required for each drug infusion increased across drug-availability sessions. Combining small doses of cocaine and remifentanil that by themselves resulted in very low rates of responding yielded rates of responding that were higher than the maximum maintained by any dose of the constituent drugs. Nevertheless, demand curve analysis demonstrated that the drug combination was equally elastic as the component drugs, indicating that it was not more effective as a reinforcer than either cocaine or remifentanil alone. This suggests that enhanced self-administration of this particular drug combination is due primarily to the drug enhancement of the potency of the other drug. The American Society for Pharmacology and Experimental Therapeutics