Life-threatening QT prolongation in a boy with attention-deficit/hyperactivity disorder on atomoxetine

As a noncentral nerve-stimulating agent blocking reuptake of noradrenalin, atomoxetine is used for treatment of attention-deficit/hyperactivity disorder (ADHD). Because it has less potential for addiction and abuse and improves core symptoms of ADHD, it is commonly prescribed in many children and adolescents internationally. Its common side effects include headache, abdominal pain, decreased appetite, and weight loss. In addition, cardiac effects such as tachycardia and hypertension have also been reported. In this case report, an 11-year-old Japanese boy with a past medical history of ADHD on atomoxetine for more than 2 years presented with a loss of consciousness. Initial electrocardiogram (ECG) showed significant QT prolongation, and 9 h later, it worsened, along with bradycardia, inversed T waves, and multiple premature ventricle contractions (PVCs). Transthoracic echocardiography showed akinesis with dilation and systolic ballooning of the left ventricle's (LV) apical segment (Takotsubo cardiomyopathy). At that point, bisoprolol and transcutaneous pacing were started. After 5 days, transcutaneous pacing was discontinued due to improvement in his cardiac rhythm. He continued to remain asymptomatic for the next year, while his QT interval returned to normal. Conclusion: This case report suggests a serious side effect of atomoxetine, and to avoid life-threatening cardiovascular events for children and adolescents with ADHD on atomoxetine, prior screening for cardiovascular conditions by ECG with close monitoring is necessary.