Effects of acute stimulant medication on cerebral metabolism in adults with hyperactivity

Recent work in our laboratory has demonstrated both global and regional reductions in cerebral glucose metabolism in adult subjects with attention-deficit hyperactivity disorder (ADHD). The purpose of the present study was to examine the effects of an acute dose of stimulant medication on cerebral metabolism in adults with ADHD using positron emission tomography with fluorodeoxyglucose-18 as the tracer. Each subject underwent scanning twice, once off-drug and again after receiving a single oral dose of either dextroamphetamine (0.25 mg/kg) or methylphenidate (0.35 mg/kg). Subjects completed behavioral self-report measures before and after the scan and performed an auditory continuous performance task during the tracer uptake period. Neither drug changed global metabolism. Both drugs increased systolic blood pressure, and dextroamphetamine improved performance on the auditory attention task. Each stimulant produced a differential pattern of increases and decreases in regional metabolism throughout the regions of interest that were sampled. Rather than increasing glucose utilization in specific brain regions with lowered metabolic rates in adults with ADHD, stimulants may act by altering glucose use throughout the brain.