From the FDA Drug Label
Cardiac Electrophysiology — The effect of atomoxetine hydrochloride on QTc prolongation was evaluated in a randomized, double-blinded, positive-(moxifloxacin 400 mg) and placebo-controlled, cross-over study in healthy male CYP2D6 poor metabolizers. A total of 120 healthy subjects were administered atomoxetine hydrochloride (20 mg and 60 mg) twice daily for 7 days. No large changes in QTc interval (i. e., increases >60 msec from baseline, absolute QTc >480 msec) were observed in the study. However, small changes in QTc interval cannot be excluded from the current study, because the study failed to demonstrate assay sensitivity. There was a slight increase in QTc interval with increased atomoxetine concentration.
The effect of atomoxetine on QT interval at night in patients with Attention Deficit Hyperactivity Disorder (ADHD) is not directly addressed in the provided drug label. The study mentioned in the label was conducted in healthy male CYP2D6 poor metabolizers, not specifically in patients with ADHD, and did not provide information on the effect of atomoxetine on QT interval at night. Therefore, no conclusion can be drawn regarding the effect of atomoxetine on QT interval at night in patients with ADHD 1.
From the Research
Atomoxetine does not typically cause QT interval prolongation at standard doses, making it generally safe from a cardiac perspective, as supported by studies such as 2. When considering the effect of atomoxetine on QT interval at night in patients with Attention Deficit Hyperactivity Disorder (ADHD), it's essential to look at the most recent and highest quality studies. The study by 2 compared once-daily morning-dosed atomoxetine, evening-dosed atomoxetine, and placebo for treating pediatric ADHD, finding that both morning and evening dosing significantly decreased core ADHD symptoms relative to placebo, with symptom improvements measured up to 24 hours later. Some key points to consider:
- Atomoxetine works differently from stimulant medications by increasing norepinephrine levels in the brain rather than affecting dopamine.
- Unlike stimulants, it provides 24-hour coverage once it reaches steady state in your system, which takes about 1-2 weeks.
- Side effects that might make nighttime dosing preferable include fatigue, drowsiness, or upset stomach.
- However, some people experience insomnia with atomoxetine, in which case morning dosing would be better.
- Always take atomoxetine as prescribed by your healthcare provider, who can help determine the optimal timing based on your individual response and side effect profile, as noted in studies like 3 and 4. It's also worth noting that atomoxetine has been shown to be effective and well-tolerated for the acute and long-term treatment of children and adolescents suffering from ADHD, as demonstrated in studies such as 5. Overall, the evidence suggests that atomoxetine is a safe and effective treatment option for ADHD, with a low risk of QT interval prolongation, as supported by the study 2.