Background: Non-medical use and abuse of prescription opioids is a significant problem in the United States. Little attention has been paid to assessing the relative psychopharmacological profile (including abuse liability-related effects) of specific prescription opioids. The purpose of this study was to directly compare the psychopharmacological profile of two widely prescribed and abused oral opioid combination products within the same subject.
Methods: Twenty non-drug-abusing volunteers participated in a crossover, randomized, double-blind study in which they received, all p.o.: placebo; 975 mg acetaminophen (ACET); 10mg oxycodone (OXY)/487 mg ACET; 20mg OXY/975 mg ACET; 15 mg hydrocodone (HYD)/487 mg ACET; and 30mg HYD/975 mg ACET. OXY and HYD doses were chosen to equate the drugs on an objective measure of opiate effects: miosis. Dependent measures were subjective, psychomotor/cognitive, reinforcing, and physiological effects, and relative potency estimates.
Results: In general, the two opioid combination products at equi-miotic doses produced similar prototypic opiate-like effects and psychomotor impairment, and of similar magnitude. The higher dose of OXY/ACET produced slightly more abuse liability-related subjective effects than the higher dose of HYD/OXY, but also produced slightly more negative effects. Neither drug at either dose functioned as a reinforcer, as measured by the Multiple Choice Procedure. Relative potency ratios indicated that OXY/ACET was approximately 1.5 times more potent than HYD/ACET.
Conclusions: Consistent with a recent study published in this journal using identical doses of HYD and OXY (without ACET) in prescription opioid abusers (Walsh, S.L., Nuzzo, P.A., Lofwall, M.R., Holtman Jr., J.R., 2008. The relative abuse liability of oral oxycodone, hydrocodone and hydromorphone assessed in prescription drug abusers. Drug Alcohol Depend. 198, 191-202), we found little difference in the pharmacodynamic effects of HYD/ACET and OXY/ACET in non-drug-abusing volunteers.