Drug preference and mood in humans: repeated assessment of d-amphetamine

Ten normal human volunteers participated in 3 identical choice experiments comparing 5 mg d-amphetamine and placebo. Each experiment consisted of 9 sessions. During the first 4 sessions of each experiment, subjects received alternatively drug or placebo. During the next 5 sessions, they were given a choice between amphetamine and placebo. Subjective effects were assessed using the Profile of Mood States (POMS) before drug was taken and 1, 3 and 6 hrs later. Subjects chose amphetamine an average of 4.0, 3.2 and 2.1 times out of 5 during each of the three experiments, in that order. Compared to placebo, amphetamine produced changes in mood as measured by the POMS including increased Vigor, Elation, Arousal and Positive Mood. Mood changes produced by amphetamine were similar across all three experiments despite the decrease in drug preference, suggesting the independence of these two measures. The results are discussed in terms of developing methods for predicting the abuse potential of psychotropic drugs.