Review of self-administration.

The reinforcing properties of drugs can be evaluated pre-clinically using self-administration procedures in laboratory animals. This paper reviews self-administration studies of the four opioid agonist/antagonist analgesics pentazocine, butorphanol, nalbuphine and buprenorphine, and compares these results to those from studies of morphine and cyclazocine. All four agonist/antagonists possess reinforcing properties under at least some test conditions. In this respect they more resemble morphine than cyclazocine. These results suggest that they all may have some potential for recreational use. On the other hand, some data point to a lower reinforcing efficacy for these agonist/antagonists than for the pure agonists such as morphine. Studies comparing the reinforcing efficacy among the agonist/antagonists are also reviewed, however more data are needed before definitive conclusions can be drawn within the class.