Common Side Effects of Strattera (Atomoxetine)
The most common side effects of Strattera include gastrointestinal symptoms (nausea, abdominal pain, vomiting), decreased appetite, somnolence, dizziness, and in adults, dry mouth, constipation, insomnia, and sexual dysfunction. 1
Most Frequent Side Effects by Age Group
Children and Adolescents
The most commonly reported adverse reactions in pediatric patients include:
- Gastrointestinal effects: Abdominal pain (13-18%), nausea (6-13%), vomiting (8-11%), and constipation (1-2%) 2, 1
- Appetite and weight: Decreased appetite is very common, with initial weight loss that typically normalizes after 2-3 years of treatment 2
- Somnolence/fatigue: Initial sedation occurs, particularly if dosage is increased too rapidly 2
- Mood changes: Mood swings (11-20%) and irritability 1
- Headache: Commonly reported 3
Adults
The most common side effects in adults differ somewhat from children:
- Gastrointestinal: Constipation (10%), dry mouth (21%), nausea (21%), abdominal pain (7%) 1
- Appetite: Decreased appetite (16%) 1
- Central nervous system: Dizziness (8%), insomnia (15%), somnolence (8%) 1
- Sexual dysfunction: Erectile dysfunction (8% of males), ejaculation delay/disorder (4% of males), decreased libido (3%) 1, 4, 5
- Urinary: Urinary hesitation (6%), dysuria (2%) 1
- Autonomic: Hyperhidrosis (4%), hot flush (3%) 1
Cardiovascular Effects
Atomoxetine causes mild increases in heart rate and blood pressure, similar to stimulants but generally clinically insignificant. 2
- Average increases: 1-2 beats per minute for heart rate and 1-4 mm Hg for blood pressure 2
- A subset of patients (5-15%) may experience more substantial increases requiring monitoring 2
- The risk of serious cardiovascular events is extremely low 2
Growth Effects
Atomoxetine is linked to temporary growth delays in the first 1-2 years of treatment, with return to expected measurements after 2-3 years on average. 2
- Decreases are most notable in children who were taller or heavier than average before treatment 2
- Atomoxetine shows fewer growth/height problems compared to stimulants 2
Serious but Rare Side Effects
Black Box Warning: Suicidal Ideation
The FDA has issued a black box warning for increased suicidal thoughts in children and adolescents taking atomoxetine. 2, 3
- This is less common but requires careful monitoring 2
Hepatotoxicity
Extremely rarely, hepatitis has been associated with atomoxetine. 2, 3
- Postmarketing data show three patients with liver-related adverse events probably related to atomoxetine 3
Priapism
Erections that won't go away (priapism) have occurred rarely during treatment. 1
- Any erection lasting more than 4 hours requires immediate medical evaluation 1
Metabolizer Status Differences
Poor CYP2D6 metabolizers experience more frequent and severe side effects compared to extensive metabolizers. 1
In Children/Adolescents (Poor Metabolizers vs Extensive Metabolizers):
- Insomnia (11% vs 6%) 1
- Weight decreased (7% vs 4%) 1
- Constipation (7% vs 4%) 1
- Depression (7% vs 4%) 1
- Tremor (5% vs 1%) 1
In Adults (Poor Metabolizers vs Extensive Metabolizers):
- Dry mouth (35% vs 17%) 1
- Decreased appetite (23% vs 15%) 1
- Erectile dysfunction (21% vs 9%) 1
- Insomnia (19% vs 11%) 1
- Hyperhidrosis (15% vs 7%) 1
Tolerability Profile
Atomoxetine is generally well tolerated, with most adverse events being mild to moderate in severity. 3, 6
- Discontinuation rates due to adverse events: 7.8-11.3% in adults vs 3.0-4.3% with placebo 4, 5
- Within nonstimulants, adverse effects of atomoxetine are less frequent and less pronounced compared to clonidine and guanfacine 2
- Atomoxetine discontinuation is well tolerated with low incidence of discontinuation-emergent adverse events 3
Key Clinical Considerations
To minimize gastrointestinal side effects, avoid rapid dose escalation and consider splitting the daily dose into morning and evening administration. 2