1. ¹Division on Substance Abuse, New York State Psychiatric Institute, College of Physicians and Surgeons of Columbia University, New York, NY, USA
2. ²Department of Psychiatry, College of Physicians and Surgeons of Columbia University, New York, NY, USA
3. ³Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, New York, NY, USA

Correspondence: Dr SD Comer, Department of Psychiatry, The New York State Psychiatric Institute, College of Physicians and Surgeons of Columbia University, 1051 Riverside Dr., Unit 120, New York, NY 10032, USA. Tel: +1 212 543 5981; Fax: +1 212 543 5991; E-mail: sdc10@columbia.edu

Received 12 January 2007; Revised 14 May 2007; Accepted 15 May 2007; Published online 20 June 2007.

Abstract

Abuse of prescription opioid medications has increased dramatically in the United States during the past decade, as indicated by a variety of epidemiological sources. However, few studies have systematically examined the relative reinforcing effects of commonly abused opioid medications. The current double-blind, placebo-controlled in-patient study was designed to compare the effects of intravenously delivered fentanyl (0, 0.0625, 0.125, 0.187, and 0.250 mg/70 kg), oxycodone (0, 6.25, 12.5, 25, and 50 mg/70 kg), morphine (0, 6.25, 12.5, 25, and 50 mg/70 kg), buprenorphine (0, 0.125, 0.5, 2, and 8 mg/70 kg), and heroin (0, 3.125, 6.25, 12.5, and 25 mg/70 kg) in morphine-maintained heroin abusers (N=8 completers maintained on 120 mg per day oral morphine in divided doses (30 mg q.i.d.)). All of the participants received all of the drugs tested; drugs and doses were administered in non-systematic order. All of the drugs produced statistically significant, dose-related increases in positive subjective ratings, such as 'I feel a good drug effect' and 'I like the drug.' In general, the order of potency in producing these effects, from most to least potent, was fentanyl>buprenorphineheroin >morphine=oxycodone. In contrast, buprenorphine was the only drug that produced statistically significant increases in ratings of 'I feel a bad drug effect' and it was the only drug that was not self-administered above placebo levels at any dose tested. These data suggest that the abuse liability of buprenorphine in heroin-dependent individuals may be low, despite the fact that it produces increases in positive subjective ratings. The abuse liabilities of fentanyl, morphine, oxycodone, and heroin, however, appear to be similar under these experimental conditions.