Objective: This secondary analysis examined the efficacy and tolerability of atomoxetine (ATX) dosed once (QD) versus twice (BID) daily in 55 children aged 6-12 with attention-deficit/hyperactivity disorder (ADHD).
Methods: The original 8-week trial was designed to assess the benefits of adding behavioral therapy to ATX. In it, all subjects were treated openly with ATX, with 50% randomly assigned to additional behavioral treatments. Every subject was started on QD dosing with a target dose of 1.2 mg/kg per day. A switch to BID dosing was allowed at study midpoint to improve tolerability and efficacy. Subjects not responding to ATX at midpoint were also given the option of 0.6 mg/kg dose increase. ADHD and oppositional defiant disorder (ODD) symptoms, global functioning, side effects, and classroom performance were measured weekly.
Results: There were 22 subjects (40%) who switched to BID dosing at midpoint (mean dose = 1.56 mg/kg per day) with the other 33 remaining on QD dosing (mean dose = 1.33 mg/kg per day). The BID group did not display any improvement in parent-rated ODD symptoms during the first 4 weeks of the study on QD dosing, but there was a significant improvement seen after the addition of the second ATX dose (p < 0.05). However, BID dosing was not associated with differential rates of change for parent-rated ADHD symptoms or impairment, teacher ratings, or other measures of classroom functioning. BID dosing was associated with decreased rates of stomachaches (p < 0.05) but more persistent appetite loss than QD dosing. The degree of improvement observed during the first half of the study in ratings of global impairment and ODD but not ADHD symptoms predicted a switch to BID dosing at midpoint (p < 0.05).
Conclusions: The addition of an afternoon dose of ATX was associated with improved control of ODD symptoms at home, with no change in school functioning.