Factors influencing the reinforcing and subjective effects of ephedrine in humans
There has been little study of the abuse liability of ephedrine, a naturally occurring drug used in medicine for thousands of years and currently sold as a “legal” stimulant. The present study measured the reinforcing and subjective effects of ephedrine in a group of 27 adults (18 females and 9 males) with no history of drug dependence. A discrete-trial choice procedure was used to assess the reinforcing effects of a single oral dose of ephedrine selected to produce a moderate subjective response in each subject (range: 37.5-75 mg). A number of variables (gender, current and past drug use, personality, and baseline mood and arousal) were examined in an attempt to identify sources of variability 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 positively associated with current use of marijuana and lower levels of baseline anxiety and hunger, as well as with lower scores on two scales measuring dimensions of the personality trait of harm avoidance. Males 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 of the same design withd-amphetamine, these results demonstrate that ephedrine produces a different profile of subjective effects and is a less efficacious reinforcer than amphetamine, suggesting that ephedrine has a lower liability for abuse.