Objective: Data from acute studies of atomoxetine in patients with attention-deficit/hyperactivity disorder suggest that a dose of approximately 1.2 mg/kg per day is required to attain a maximal symptom response. However, lower doses could be effective during maintenance treatment, which would reduce drug exposure and potential problems related to tolerability during chronic treatment.
Methods: Patients 6 to 16 years of age who had a robust response to an initial acute trial of atomoxetine were assigned randomly under double-blind conditions to continue treatment for up to 8 months with either the dose to which they had responded acutely (1.2-1.8 mg/kg per day, N = 116, continued same dose) or a lower dose (0.5 mg/kg per day, N = 113, low dose). The primary outcome measure was relapse, defined as an Attention-Deficit/Hyperactivity Disorder Rating Scale-IV-Parent Version: Investigator-Administered and Scored total score returned to > or = 90% of the original baseline value (before acute treatment) for 2 consecutive visits. Mean change in Attention-Deficit/Hyperactivity Disorder Rating Scale total score was assessed as a secondary outcome.
Results: At randomization, symptom severity was low and similar in both groups. At end point, relapse rates did not differ between the groups. Mean change in Attention-Deficit/Hyperactivity Disorder Rating Scale total score from the conclusion of acute treatment to end point also was not different between groups. Reports of affective lability were higher in the patients in the low-dose group. Also, increases in heart rate (compared with when atomoxetine was started) were higher in the patients in the continued same-dose group than in the low-dose group. Finally, increases in weight over the course of the trial were greater for the low-dose group than the continued same-dose group.
Conclusions: For patients who experience a robust response to atomoxetine, it may be possible to retain the response during maintenance treatment with a reduced dose of atomoxetine.