What are the side effects of atomoxetine (Strattera) in children?

Side Effects of Atomoxetine in Children

The most common side effects of atomoxetine in children include nausea, vomiting, fatigue, decreased appetite, abdominal pain, and somnolence, with more serious concerns including risk of suicidal ideation, liver damage, and cardiovascular effects. 1, 2

Common Side Effects

Atomoxetine (Strattera) commonly causes several gastrointestinal and neurological side effects in children:

• Gastrointestinal effects:

  • Nausea
  • Vomiting
  • Abdominal pain
  • Decreased appetite
  • Constipation
  • Dyspepsia

• Neurological effects:

  • Fatigue
  • Somnolence (drowsiness)
  • Dizziness
  • Mood swings

These side effects typically appear early in treatment and often diminish over time 1, 2.

Serious Side Effects and Warnings

1. Suicidal Ideation

• Analysis of twelve placebo-controlled trials showed increased risk of suicidal thoughts in children and adolescents taking atomoxetine 1
• Requires close monitoring for suicidality, clinical worsening, and unusual behavior changes, especially during the first few months of treatment or with dose changes 1, 2

2. Liver Damage

• Can cause severe liver injury in some patients
• Warning signs include:
  • Itching
  • Right upper abdominal pain
  • Dark urine
  • Yellowing of skin or eyes
  • Unexplained flu-like symptoms 2

3. Cardiovascular Effects

• Can cause increases in blood pressure and heart rate 1, 2
• Requires regular monitoring of cardiovascular parameters
• Contraindicated in children with significant cardiac abnormalities or preexisting cardiovascular diseases 1

4. Growth Effects

• Initial period of weight loss followed by normal rate of weight gain 3
• May affect height growth temporarily, but long-term studies suggest return to normal growth patterns 4

5. Other Serious Concerns

• Potential for new psychotic or manic symptoms 1, 5
• Possible allergic reactions 1
• Effects on urine outflow 1
• Priapism (prolonged, painful erections requiring immediate medical attention) 2
• Aggression or hostility 1, 6

Special Populations and Considerations

Metabolizer Status

• Approximately 7% of the population are poor metabolizers of atomoxetine due to CYP2D6 enzyme variations
• These patients have higher plasma levels and longer half-lives of the medication
• May experience more pronounced side effects 1

Dosing Considerations

• Starting dose typically 0.5 mg/kg/day
• Target dose 1.2 mg/kg/day (maximum 1.4 mg/kg/day or 100 mg/day, whichever is lower) 1, 5
• Dose-related side effects may occur, with higher discontinuation rates at doses exceeding 1.5 mg/kg/day 7

Drug Interactions

• Caution with medications that inhibit CYP2D6 (e.g., paroxetine)
• Absolutely contraindicated with MAOIs (monoamine oxidase inhibitors) 5, 2
• Some selective serotonin reuptake inhibitors can elevate serum atomoxetine levels 1

Monitoring Recommendations

• Regular assessment of:

  • Blood pressure and heart rate
  • Height and weight
  • Liver function
  • Mental status, particularly for suicidal ideation
  • Behavior changes
  • Side effect emergence 1, 5, 2

• Follow-up within 2-4 weeks after medication initiation 5

Atomoxetine is generally well-tolerated in most children, with serious adverse events being rare. However, the potential for suicidal ideation, liver damage, and cardiovascular effects necessitates careful monitoring, especially during the initial treatment period and with dose adjustments 1, 2, 4.