Strattera (Atomoxetine) Side Effects
Strattera causes common gastrointestinal and neuropsychiatric side effects that typically appear within the first week of treatment, with the most frequent being nausea, decreased appetite, abdominal pain, fatigue, and somnolence in both children and adults. 1, 2
Most Common Side Effects by Population
Children and Adolescents (≥5% incidence and twice placebo rate):
- Nausea (10% vs 5% placebo) 2
- Vomiting (11% vs 6% placebo) 2
- Fatigue (8% vs 3% placebo) 2
- Decreased appetite (16% vs 4% placebo) 2
- Abdominal pain (18% vs 10% placebo) 2
- Somnolence (11% vs 4% placebo) 2
Adults (≥5% incidence and twice placebo rate):
- Constipation, dry mouth, nausea, decreased appetite, dizziness, erectile dysfunction, and urinary hesitation 2
- Dry mouth occurs in 21% of adults 2
- Erectile dysfunction affects 21% of male patients 2
Critical Safety Warnings
Black Box Warning - Suicidal Ideation:
Atomoxetine carries an FDA black box warning for increased suicidal thoughts in children and adolescents. 1 Analysis of 12 placebo-controlled trials showed greater risk of suicidal ideation during treatment in pediatric patients. 1 All children must be monitored closely for suicidality, clinical worsening, and unusual behavioral changes, especially during the first few months or at dose changes. 1 This risk was not observed in adult trials. 1
Cardiovascular Effects:
- Increased heart rate and blood pressure occur but are typically small and clinically insignificant 1, 3
- Approximately 5-10% of patients experience potentially clinically important changes (≥20 bpm heart rate or ≥15-20 mmHg blood pressure) 2
- These increases occur early in therapy, stabilize, and return toward baseline upon discontinuation 3
- Obtain personal and family cardiac history before initiating treatment; perform ECG if risk factors present 1
Hepatotoxicity:
Extremely rare hepatitis has been associated with atomoxetine use. 1 Postmarketing data identified three patients with liver-related adverse events probably related to atomoxetine. 4
Timing of Side Effects
Most adverse events appear within the first week of treatment. 5 Resolution times vary considerably:
- Median resolution time ranges from 3 to 53 days after discontinuation 5
- Some effects resolve rapidly while others have a more lingering course 5
- Male sexual side effects may take longer to resolve 5
- Cardiovascular parameters (BP and HR) return to baseline upon discontinuation 5
Gastrointestinal Effects
Initial somnolence and gastrointestinal symptoms are common, particularly if dosage is increased too rapidly. 1 Common GI effects include:
- Nausea (7% adults, 10% children) 2
- Vomiting (11% children, 1% adults) 2
- Abdominal pain (17% children, 13% adults) 2
- Constipation (more common in adults at 11%) 2
Genitourinary Effects
Urinary hesitation and retention occur more commonly in men than women. 6 Specific effects include:
- Urinary hesitation/decreased urine flow 2
- Urinary retention (6% in poor metabolizers vs 1% in extensive metabolizers) 2
- Erectile dysfunction (21% in poor metabolizers vs 9% in extensive metabolizers) 2
- Ejaculation disorder (6% in poor metabolizers vs 2% in extensive metabolizers) 2
- Rarely, priapism 1
- Discontinuation typically leads to rapid resolution 6
Growth Effects
Atomoxetine is linked to growth delays in the first 1-2 years of treatment, with return to expected measurements after 2-3 years on average. 1 Decreases were observed among those who were taller or heavier than average before treatment. 1
Psychiatric Effects Beyond Suicidality
- Mood swings (2% children) 2
- Irritability (6% children) 2
- Aggression or hostility (warnings exist for all ages) 1
- Emergent psychotic or manic symptoms (warnings exist) 1
Poor Metabolizer Considerations
Approximately 7% of the population are poor CYP2D6 metabolizers with significantly higher plasma levels and longer half-lives, leading to increased adverse effects. 1, 2 Poor metabolizers experience statistically higher rates of:
- Vision blurred (4% vs 1% extensive metabolizers) 2
- Dry mouth (35% vs 17%) 2
- Tremor (5% vs 1%) 2
- Insomnia (19% vs 11%) 2
- Hyperhidrosis (15% vs 7%) 2
Discontinuation Rates
- 3.0% of children/adolescents discontinued due to adverse events in acute trials (vs 1.4% placebo) 2
- 11.3% of adults discontinued (vs 3.0% placebo) 2
- Poor metabolizers have higher discontinuation rates (11.2% vs 6.3% extensive metabolizers) 2
- Atomoxetine discontinuation is generally well tolerated with low incidence of discontinuation-emergent adverse events 4
Clinical Monitoring Recommendations
Patients should be explicitly educated and monitored for genitourinary adverse events, as they may not be spontaneously reported. 6 Monitor: