In the six-week trial, investigators found that symptom reduction lasted into the evening without causing insomnia. Previous studies have shown no significant differences in insomnia between atomoxetine and placebo.

Positive findings included significant reduction in inattention, hyperactivity, and impulsivity as assessed by parents, teachers, and clinical investigators. In addition, parent reports, using a diary scale developed by the drug manufacturer, suggested atomoxetine continued to work late in the day, significantly reducing inattention during late afternoon and early evening, and reducing difficulties with the transition to bedtime.

"Effective treatment of attention deficit hyperactivity disorder involves not only a reduction of symptoms, but also an improvement in social and family function," said study coauthor Jeffrey Newcorn, M.D. "A treatment that provides symptom control into the evening has the potential to significantly improve family interactions."

Exclusion criteria for the current study included serious medical illness, a history of psychosis or bipolar disorder, alcohol or drug abuse within the past three months, and ongoing use of psychoactive medications other than the study drug.

The primary measure of symptom response was assessed with use of the Attention Deficit Hyperactivity Disorder Rating Scale-IV-Parent Version: Investigator Administered, an 18-item scale based on an interview with the patient's primary caregiver. Each item on the scale corresponds to one of the 18 diagnostic criteria. In addition, a 13-item parent-rated diary was used to assess efficacy during evening and early morning periods. Symptoms assessed with the diary included evening and early morning inattentiveness and distractibility, ability to concentrate on structured tasks, hyperactivity and impulsivity, and oppositionality. The study also used the Conners' Parent and Conners' Teacher Rating Scales.

Overall Scale scores fell by an average of 12.8 points for patients randomized to atomoxetine compared with 5.0 points for patients on placebo. Improvements were measurable for active-treatment patients at one week and at all subsequent visits. Superiority to placebo was also demonstrated with the other outcome measures.

Interpretation of the results is limited by several factors. This study did not include a twice-daily dosing arm, and thus no direct comparison of the relative efficacy of once-daily versus twice-daily administration can be definitively determined. Also, the dose range used in this study was based on the results of a dose-response study that employed twice-daily dosing; it is possible that a different range would be optimal for once-daily dosing.

Study data indicate that the drug was safe and well tolerated at the dosage level. There were no statistically significant differences in the number of discontinuations between atomoxetine and placebo. Only two patients receiving atomoxetine discontinued use because of adverse events (2 percent) compared to one patient in the placebo group (1 percent). The most common side effects for atomoxetine (greater than 16 percent) were headache, rhinitis, abdominal pain, and decreased appetite.