What are the side effects of Strattera (atomoxetine)?

Strattera (Atomoxetine) Side Effects

The most common side effects of Strattera (atomoxetine) include gastrointestinal symptoms (nausea, vomiting, abdominal pain), decreased appetite, fatigue, somnolence, and mood changes, with more serious concerns including cardiovascular effects, growth effects in children, and rare but significant risks of suicidal ideation and liver injury. 1, 2

Common Side Effects

In Children and Adolescents:

• Gastrointestinal effects:

  • Abdominal pain (17-18% vs 7-13% with placebo)
  • Vomiting (11-14% vs 4-8% with placebo)
  • Nausea (7-13% vs 4-6% with placebo)
  • Constipation (2% vs 1% with placebo) 2

• Neurological/Psychiatric effects:

  • Fatigue (6-9% vs 2-4% with placebo)
  • Somnolence/sedation (8-10% vs 3-5% with placebo)
  • Mood swings (2% vs 0-1% with placebo) 2

• Other common effects:

  • Decreased appetite (16% vs 3% with placebo)
  • Weight loss (2-7%, more common in poor metabolizers) 1, 2

In Adults:

• Gastrointestinal effects:

  • Dry mouth (20-26% vs 5-7% with placebo)
  • Nausea (12-26% vs 5-8% with placebo)
  • Constipation (7-11% vs 3-4% with placebo) 2, 3

• Sexual side effects:

  • Erectile dysfunction (8% vs 1% with placebo)
  • Ejaculation disorders (4% vs 1% with placebo)
  • Decreased libido (3% vs 1% with placebo) 2, 3

• Urinary effects:

  • Urinary hesitation (6% vs 1% with placebo)
  • Dysuria (2% vs 0% with placebo) 2

Serious Side Effects and Warnings

Cardiovascular Effects

• Increases in heart rate and blood pressure (typically modest but clinically significant)
• Regular monitoring of heart rate and blood pressure is recommended by the American Academy of Pediatrics 4
• Use with caution in patients with hypertension or significant cardiovascular disorders 5

Psychiatric Effects

• Suicidal ideation: Black box warning exists for increased risk of suicidal ideation in children and adolescents
• Analyses of twelve placebo-controlled trials showed greater risk in participants receiving atomoxetine compared to placebo
• Close monitoring is required, especially during the first few months of treatment or at times of dose changes 1
• May cause emergent psychotic or manic symptoms 1

Growth Effects

• Can cause initial slowing of height and weight gain in children
• Regular monitoring of height and weight is recommended 4
• Growth effects typically normalize with continued treatment 6

Hepatic Effects

• Rare but serious liver injury has been reported
• Postmarketing data showed three patients with liver-related adverse events deemed probably related to atomoxetine 6

Metabolizer Status Considerations

• Side effects may be more pronounced in poor CYP2D6 metabolizers (approximately 7% of the population)
• Poor metabolizers experience:
  • Higher plasma levels and longer half-lives
  • More frequent insomnia (11% vs 6%)
  • More frequent constipation (7% vs 4%)
  • More frequent depression (7% vs 4%)
  • More frequent tremor (5% vs 1%) 1, 2

Monitoring Recommendations

1. Cardiovascular monitoring:

   • Regular checks of heart rate and blood pressure 4
   • More frequent monitoring in patients with pre-existing cardiovascular conditions

2. Growth monitoring in children:

   • Regular height and weight measurements
   • Consider dose adjustments if significant growth suppression occurs 4

3. Psychiatric monitoring:

   • Watch for emergence of suicidal thoughts or behaviors, especially in the first few months
   • Monitor for signs of psychosis, mania, or aggression 1

4. Hepatic function:

   • Be alert for signs of liver dysfunction (jaundice, dark urine, right upper quadrant pain)
   • Consider liver function tests if symptoms develop

Special Considerations

• Pregnancy: Limited data available; caution advised due to possible increased risk for spontaneous abortion 4
• Breastfeeding: Likely present in breast milk; caution advised 4
• Abuse potential: Unlike stimulants, atomoxetine has negligible risk of abuse or misuse 6, 7
• Sleep effects: Less likely than stimulants to exacerbate sleep disorders 6

Atomoxetine should be started at lower doses and titrated gradually, with consideration of lower doses in poor metabolizers. The medication can be administered once daily or split into two evenly divided doses, with a maximum recommended dosage of 1.4 mg/kg/day or 100 mg/day, whichever is lower 1, 4.