The acute effects of d-amphetamine and methamphetamine on attention and psychomotor performance

Rationale: It is not clear how the deleterious effects of amphetamines on driving performance are mediated in terms of select cognitive processes. Objectives: The current three separate experiments assessed the acute effects of an oral dose of either 0.42-mg/kg d-amphetamine, d,l-methamphetamine and d-methamphetamine on driving-related cognitive functions in a total of 60 healthy non-fatigued adults. Materials and Methods: Three separate repeated measures counterbalanced, double-blind, placebo-controlled designs were employed in which 20 volunteers completed two treatment conditions, either d-amphetamine, d,l-methamphetamine or d-methamphetamine and placebo. Performance was assessed on a range of attentional, psychomotor and perceptual speed tasks. Results: Mean blood concentrations at 120-, 170- and 240-min postdrug administration were 83, 98 and 96 ng/ml, respectively, for d-amphetamine, 90, 95 and 105 ng/ml, respectively, for d,l-methamphetamine and 72, 67 and 59 ng/ml, respectively, for d-methamphetamine. The amphetamines, in general, improved various aspects of attention (Digit Vigilance, Digit Symbol Substitution Test and Movement Estimation Performance) with some evidence to suggest possible enhancement in psychomotor functioning (Tracking ability) and perceptual speed (Inspection Time). Conclusions: The current series of studies primarily provides evidence of low-level amphetamine-related enhancement of function; however, it also provides evidence of less conservative movement estimation that might contribute to amphetamine-related road fatalities.