Abstract

The comparative effects of d-amphetamine, l-amphetamine, and methylphenidate were assessed in 16 normal subjects, using a double-blind, crossover placebo-controlled design. Within the dose range tested, the efficacy ratio of d-amphetamine:l-amphetamine was about 2:1, and graphic presentation of dose response scores indicated a relatively small difference in potency between the amphetamine isomers. Methylphenidate was intermediate in efficacy between d-amphetamine and l-amphetamine. The efficacy ratios for d-amphetamine:l-amphetamine on increasing euphoric mood in man were similar to the previously reported ratios of there two isomers in inducing or exacerbating psychosis in humans. These findings do not support the suggestion, made by Snyder and others, that the differential effects of d-amphetamine vs. l-amphetamine on a specific type of behavior in man could be utilized to infer the predominance of noradrenergic vs. dopaminergic mediation of amphetamine's effects on this behavior.