What should be done if an adolescent experiences heart flutters while taking Strattera (atomoxetine)?

Strattera and Heart Flutters in Adolescents

If an adolescent experiences heart flutters (palpitations) while taking Strattera (atomoxetine), the medication should be temporarily held and the patient should undergo prompt cardiac evaluation including ECG, vital signs assessment, and detailed cardiovascular history before any decision to continue or discontinue treatment. 1

Immediate Clinical Actions

Discontinue atomoxetine immediately and perform the following assessments:

• Obtain a 12-lead ECG to evaluate for QRS widening, QT prolongation, or arrhythmias 1, 2
• Measure heart rate and blood pressure in both supine and standing positions to assess for orthostatic changes 3
• Document the timing, frequency, and characteristics of the palpitations relative to dosing 1
• Review all concomitant medications, particularly CYP2D6 inhibitors (such as paroxetine, fluoxetine) which can increase atomoxetine exposure 2-4 fold 1, 4

Risk Assessment Framework

The FDA labeling for atomoxetine explicitly contraindicates its use in patients with severe cardiovascular disorders that might deteriorate with clinically important increases in heart rate and blood pressure 1. Before restarting, you must determine:

Personal cardiac history:

• Structural cardiac abnormalities (atomoxetine generally should not be used in adolescents with known serious structural cardiac abnormalities, cardiomyopathy, or serious heart rhythm abnormalities) 1
• History of syncope, chest pain, or exercise intolerance 1
• Prior arrhythmias or conduction abnormalities 1

Family cardiac history:

• Sudden cardiac death in first-degree relatives under age 50 1
• Inherited arrhythmia syndromes (Long QT, Brugada) 1
• Cardiomyopathies 1

Understanding the Cardiovascular Effects

Atomoxetine causes statistically significant but generally clinically minor increases in heart rate (mean 5-10 bpm) and blood pressure (mean 2-4 mmHg) in most patients 4, 5. However, individual responses vary considerably, and some patients experience more pronounced effects 3.

Critical distinction: While large population studies show no increased risk of serious cardiovascular events including sudden cardiac death in ADHD patients taking atomoxetine 5, 6, individual patients with underlying cardiac vulnerabilities may be at higher risk 1.

CYP2D6 Metabolism Considerations

Approximately 7-10% of Caucasians are CYP2D6 poor metabolizers, resulting in 10-fold higher atomoxetine plasma concentrations 1, 4. Poor metabolizers experience:

• Greater cardiovascular side effects including palpitations 4, 3
• Higher rates of adverse events overall 4
• Need for dose reduction to 50% of standard dosing if treatment continues 1

If the patient is taking a strong CYP2D6 inhibitor (paroxetine, fluoxetine, quinidine, bupropion), this creates a pharmacokinetic profile similar to poor metabolizers 1, 4. Consider whether the palpitations began after starting such medications 7.

Decision Algorithm for Continuation

Do NOT restart atomoxetine if:

• ECG shows QRS widening >100ms, QTc >460ms, or any arrhythmia 1, 2
• Patient has structural heart disease, cardiomyopathy, or serious rhythm abnormalities 1
• Palpitations were associated with syncope, chest pain, or dyspnea 1
• Family history reveals sudden cardiac death or inherited arrhythmia syndromes 1

May consider restarting at reduced dose if:

• ECG is completely normal 1
• Palpitations were isolated, brief, and not associated with other symptoms 4
• No personal or family cardiac risk factors identified 1
• Patient is not taking CYP2D6 inhibitors, or these can be discontinued 1
• Cardiology consultation supports continuation 1

If restarting, reduce dose by 50% and titrate slowly with weekly vital sign monitoring 1. Consider checking atomoxetine plasma levels if available 4.

Alternative Treatment Considerations

Given the cardiovascular concerns, consider switching to:

• Stimulant medications (methylphenidate, amphetamines) which have similar small increases in heart rate and blood pressure but extensive safety data showing no increased risk of serious cardiovascular events in properly screened patients 5, 6
• Alpha-2 agonists (guanfacine-XR, clonidine-XR) which actually decrease heart rate and blood pressure 5
• Behavioral interventions as monotherapy or adjunct 8

Common Pitfalls to Avoid

• Do not dismiss palpitations as "anxiety" without cardiac evaluation—atomoxetine can cause genuine cardiovascular effects requiring assessment 1, 3
• Do not restart at full dose—if continuation is appropriate, reduce dose by 50% initially 1
• Do not overlook drug interactions—CYP2D6 inhibitors dramatically increase atomoxetine exposure 1, 4
• Do not assume all palpitations are benign—while serious events are rare, individual risk stratification is essential 1, 5