Factors influencing the reinforcing and subjective effects of d-amphetamine in humans

The reinforcing and subjective effects of oral d-amphetamine (AMP) were studied in a group of non-drug abusing adults (16 males, 13 females). A discrete-trial choice procedure was used to assess the reinforcing effects of a single dose of AMP (range 7.5-20mg across subjects). A number of factors (gender, current and past drug use, personality, motor activity, and baseline mood state and psychophysiological and sensory indices of arousal) were examined in an attempt to explain both within- and between-subject variability in response to AMP. Of the 29 subjects, 11 chose AMP on either two or three out of a possible three occasions. Cigarette smokers reported stronger aversive responses to AMP and chose the drug significantly less often than non-smokers. Subjects with a history of non-medical stimulant use reported less subjective response to AMP than subjects without such history. Within-subject variability in AMP choice was related to variability in subjective response to the drug across choice trials, as well as to variability in baseline mood: AMP was more likely to be chosen when subjects were more aroused and in a more positive mood at the time of the choice. These results provide new information regarding factors that may be relevant in determining individual differences in vulnerability to abuse of psychomotor stimulants.