Side Effects of Strattera (Atomoxetine)
The most common side effects of Strattera include decreased appetite, nausea, vomiting, fatigue, abdominal pain, somnolence, and initial gastrointestinal symptoms, with most being mild to moderate and often transient. 1, 2, 3
Most Common Side Effects in Children and Adolescents
The following side effects occur in ≥5% of pediatric patients and at least twice the rate of placebo 3:
- Nausea (10% vs 5% placebo) 3
- Vomiting (11% vs 6% placebo) 3
- Decreased appetite (16% vs 4% placebo) 3
- Abdominal pain (18% vs 10% placebo) 3
- Fatigue (8% vs 3% placebo) 3
- Somnolence (11% vs 4% placebo) 3
Additional common side effects (≥2% and greater than placebo) include headache (19%), dizziness (5%), irritability (6%), weight decrease (3%), and rash (2%) 3.
Most Common Side Effects in Adults
Adult patients experience a similar but distinct profile 3, 4, 5:
- Dry mouth (significantly more common than placebo) 4, 5
- Insomnia (significantly more common than placebo) 4, 5
- Nausea (significantly more common than placebo) 4, 5
- Decreased appetite 4, 5
- Constipation 4, 5
- Dizziness 4, 5
- Sweating 4, 5
- Dysuria (urinary difficulties) 4, 5
- Sexual problems 4, 5
- Palpitations 4, 5
Cardiovascular Effects
Atomoxetine causes modest, statistically significant increases in heart rate and blood pressure that are generally well tolerated. 1, 4, 5
- Approximately 5-10% of pediatric patients experience potentially clinically important changes in heart rate (≥20 beats/min) or blood pressure (≥15-20 mmHg) 1, 3
- These cardiovascular effects gradually decrease upon cessation of treatment 4, 5
- Blood pressure and pulse should be monitored at baseline and regularly during treatment 2
Serious but Rare Side Effects
Black Box Warning: Suicidal Ideation
The FDA has issued a black box warning for increased risk of suicidal ideation in children and adolescents taking atomoxetine. 1, 2, 6
- Close monitoring is essential, especially during the first few months of treatment or with dose changes 2, 6
- Patients should be systematically assessed for suicidal thoughts at each visit 2
Hepatotoxicity
Rare but serious liver injury can occur with atomoxetine. 7
- Postmarketing data show three patients had liver-related adverse events deemed probably related to atomoxetine 7
- This is extremely rare but requires awareness 7
Seizures
Seizures were reported in 0.2% (12/5073) of children in clinical trials 3. Among poor CYP2D6 metabolizers, the seizure risk was 0.3% compared to 0.2% for extensive metabolizers 3.
Differences Between CYP2D6 Metabolizer Types
Poor CYP2D6 metabolizers experience significantly higher rates of adverse effects due to 10-fold higher drug exposure. 2, 3
The following side effects occur significantly more frequently in poor metabolizers 3:
- Insomnia (11% vs 6% in extensive metabolizers)
- Weight decrease (7% vs 4%)
- Constipation (7% vs 4%)
- Depression (7% vs 4%)
- Tremor (5% vs 1%)
- Sedation (4% vs 2%)
Approximately 7% of Caucasians and 2% of African Americans are poor CYP2D6 metabolizers 2.
Growth Effects
Initial loss in expected height and weight occurs among atomoxetine recipients, but this eventually returns to normal in the longer term. 7
- Height and weight should be tracked regularly during treatment 2
- No significant changes in weight and height gain were reported over long-term follow-up 8
Discontinuation Rates Due to Side Effects
In acute pediatric placebo-controlled trials, 3% of atomoxetine patients discontinued due to adverse reactions compared to 1.4% of placebo patients 3. In adult trials, 11.3% of atomoxetine patients discontinued compared to 3.0% of placebo patients 3.
For all studies including long-term trials, 6.3% of extensive metabolizers and 11.2% of poor metabolizers discontinued due to adverse reactions 3.
Important Clinical Considerations
Most side effects are mild to moderate, transient, and responsive to dose adjustments or timing changes. 1, 7, 8
- Gastrointestinal side effects are particularly common if dosage is increased too rapidly 1, 2
- Initial somnolence often improves with continued treatment 1, 2
- There is no evidence of symptom rebound or acute discontinuation syndrome when stopping atomoxetine 8
- Atomoxetine can be discontinued abruptly without tapering, unlike alpha-2 agonists 2
Atomoxetine requires 6-12 weeks to achieve full therapeutic effect, so patience is needed during initial treatment while monitoring for side effects. 2