FACTORS INFLUENCING THE REINFORCING AND SUBJECTIVE EFFECTS OF EPHEDRINE IN HUMANS

There has been little study of the abuse liability of ephedrine, a nat urally occurring drug used in medicine for thousands of years and curr ently sold as a ''legal'' stimulant. The present study measured the re inforcing and subjective effects of ephedrine in a group of 27 adults (18 females and 9 males) with no history of drug dependence. A discret e-trial choice procedure was used to assess the reinforcing effects of a single oral dose of ephedrine selected to produce a moderate subjec tive response in each subject (range: 37.5-75 mg). A number of variabl es (gender, current and past drug use, personality, and baseline mood and arousal) were examined in an attempt to identify sources of variab ility in response to ephedrine. Of the 27 subjects, 5 chose ephedrine on either 2 or 3 out of a possible 3 occasions; overall, ephedrine was chosen on 17% of occasions. In the group as a whole, ephedrine had no effect on ratings of drug liking, but did increase ratings of ''high' ' and scores on the MBG (''euphoria'') scale of the Addiction Research Center Inventory. Ephedrine also increased scores on a number of mood scales reflecting CNS stimulation and anxiety. Ephedrine choice was p ositively associated with current use of marijuana and lower levels of baseline anxiety and hunger, as well as with lower scores on two scal es measuring dimensions of the personality trait of harm avoidance. Ma les and females differed in their response to ephedrine - males chose ephedrine more frequently than females and showed a more positive mood response to the drug. When compared to the results of a prior study o f the same design with d-amphetamine, these results demonstrate that e phedrine produces a different profile of subjective effects and is a l ess efficacious reinforcer than amphetamine, suggesting that ephedrine has a lower liability for abuse.