Discriminative-stimulus and participant-rated effects of methylphenidate, bupropion, and triazolam in d-amphetamine-trained humans

The discriminative-stimulus and participate-rated effects of a range of doses of d-amphetamine (2.5-20 mg), methylphenidate (5-40 mg), bupropion (50-400 mg), and triazolam (0.0625-0.5 mg)were tested in 5 humans trained to discriminate between oral d-amphetamine (20 mg) and placebo. d-Amphetamine and methylphenidate generally dose dependently increased drug-appropriate responding. Bupropion and triazolam on average occasioned less than or equal to 40% drug-appropriate responding. d-Amphetamine, methylphenidate, and bupropion produced stimulant-like participant-rated effects, while triazolam produced sedative-like effects. These results further demonstrate-that the acute behavioral effects of d-amphetamine and methylphenidate overlap extensively in humans, which is concordant with preclinical studies. Bupropion produced some d-amphetamine-like, participant-rated drug effects but did not occasion significant levels of d-amphetamine-appropriate responding. These findings are concordant with previous findings of a dissociation between the discriminative-stimulus and participant-rated effects of drugs.