Comparison of the subjective, physiological, and psychomotor effects of atomoxetine and methylphenidate in light drug users

Abstract

This study compared the subjective, physiological, and psychomotor effects of atomoxetine and methylphenidate with placebo in healthy volunteers. Sixteen non-dependent light drug users participated in six experimental sessions, receiving placebo, atomoxetine (20, 45 and 90 mg) and methylphenidate (20 and 40 mg) using a double-blind, Latin square design. Subjective drug effects were assessed using Visual Analog Scales (VAS), the Addiction Research Center Inventory (ARCI) and Adjective Rating Scales (ARS). Psychomotor performance was evaluated using the Digit Symbol Substitution Test (DSST). Physiological measures were also collected throughout the sessions. Assessments were conducted before drug administration and 30, 60, 90, 120, 150, 180 and 240 min following dosing. Forty milligrams methylphenidate produced significant increases on the stimulant portions of the VAS and ARS and the benzedrine, amphetamine, morphine-benzedrine and lysergic acid diethylamine (LSD) subscales of the ARCI relative to placebo. Ninety mg atomoxetine was reported to be unpleasurable relative to placebo as indicated by significant increases on the ‘bad’ and ‘sick’ portions of the VAS, and on the LSD subscale of the ARCI. Compared with placebo, both methylphenidate doses significantly increased systolic blood pressure (BP) and heart rate (HR). For atomoxetine, 90 mg increased diastolic BP, 45 and 90 mg increased systolic BP, and all three doses increased HR relative to placebo. Neither compound produced significant differences from placebo on DSST performance. These results suggest that atomoxetine does not induce subjective effects similar to methylphenidate and suggest that it is unlikely that atomoxetine will have abuse liability.