What is the recommended dosage of atomoxetine (Strattera)?

Atomoxetine Dosing for ADHD

For children and adolescents ≤70 kg, start atomoxetine at 0.5 mg/kg/day and increase after a minimum of 3 days to a target dose of 1.2 mg/kg/day (maximum 1.4 mg/kg/day or 100 mg/day, whichever is less); for those >70 kg and adults, start at 40 mg/day and increase after 3 days to 80 mg/day, with possible escalation to 100 mg/day after 2-4 weeks if response is inadequate. 1

Initial Dosing Strategy

Children and Adolescents ≤70 kg

• Starting dose: 0.5 mg/kg/day 1
• Target dose: 1.2 mg/kg/day, reached after minimum 3 days 1
• Maximum dose: 1.4 mg/kg/day or 100 mg/day, whichever is less 1
• Administration: Can be given as single morning dose OR divided into two doses (morning and late afternoon/early evening) 1

Children and Adolescents >70 kg and Adults

• Starting dose: 40 mg/day 1
• Target dose: 80 mg/day, reached after minimum 3 days 1
• Maximum dose: 100 mg/day after 2-4 additional weeks if optimal response not achieved 1
• Administration: Single morning dose OR divided doses 1

Dosing Adjustments for Special Populations

Hepatic Impairment

• Moderate hepatic insufficiency (Child-Pugh Class B): Reduce initial and target doses to 50% of normal 1
• Severe hepatic insufficiency (Child-Pugh Class C): Reduce initial and target doses to 25% of normal 1

CYP2D6 Poor Metabolizers or Concurrent Strong CYP2D6 Inhibitors

When using strong CYP2D6 inhibitors (paroxetine, fluoxetine, quinidine) or in known CYP2D6 poor metabolizers:

• Children/adolescents ≤70 kg: Start at 0.5 mg/kg/day; increase to 1.2 mg/kg/day only if symptoms fail to improve after 4 weeks and initial dose is well tolerated 1
• Children/adolescents >70 kg and adults: Start at 40 mg/day; increase to 80 mg/day only if symptoms fail to improve after 4 weeks and initial dose is well tolerated 1

Administration Considerations

• Food: May be taken with or without food 1
• Capsule integrity: Must be swallowed whole; do not open capsules 1
• Discontinuation: Can be stopped without tapering 1
• Split dosing rationale: Dividing into two doses may reduce gastrointestinal side effects, particularly if dosage is increased too rapidly 2, 3

Monitoring Timeline and Expectations

Onset of Action

• Full therapeutic effect: 6-12 weeks required 3
• Initial assessment: Evaluate response after 6-12 weeks of treatment 3
• This delayed onset contrasts sharply with stimulants, which have rapid effects 3

Vital Sign Monitoring

• Blood pressure and heart rate: Monitor regularly, as atomoxetine can increase HR and BP 2, 3
• Cardiovascular screening: Obtain personal and family cardiac history before initiating treatment, including history of sudden death, Wolff-Parkinson-White syndrome, hypertrophic cardiomyopathy, and long QT syndrome 2
• ECG consideration: Perform if cardiac risk factors are present 2

Psychiatric Monitoring

• Suicidal ideation: FDA black box warning for increased risk in children and adolescents; monitor closely especially during first few months or with dose changes 2, 3
• Bipolar disorder screening: Screen for personal or family history of bipolar disorder, mania, or hypomania before starting 1

Common Adverse Effects to Anticipate

• Gastrointestinal: Decreased appetite, nausea, vomiting, abdominal pain (especially with rapid dose escalation) 2, 3
• Neurological: Initial somnolence, headache, dizziness, fatigue 2, 3
• Growth: Potential growth delays in first 1-2 years with return to expected measurements after 2-3 years 2
• Hepatic: Extremely rare hepatitis 2

Clinical Positioning

When to Use Atomoxetine as First-Line

• Substance abuse risk: Patients with comorbid or at-risk substance use disorders 3
• Tic disorders: Patients with Tourette's syndrome or tics 3
• Continuous coverage needed: Patients requiring "around-the-clock" symptom control without stimulant peaks and valleys 3
• Sleep disturbances: Patients experiencing sleep problems on stimulants, particularly those with autism spectrum disorder comorbidity 3

Efficacy Comparison

• Effect size: Approximately 0.7 compared to stimulants' effect size of 1.0 2
• Clinical response: In research trials, 1.2 mg/kg/day showed no additional benefit compared to 1.8 mg/kg/day 4
• Maintenance dosing: Doses of 1.2-1.8 mg/kg/day demonstrated sustained efficacy in long-term studies 1

Safety Limits

• Single dose safety: Doses over 120 mg have not been systematically evaluated 1
• Total daily dose safety: Doses above 150 mg have not been systematically evaluated 1
• No evidence for higher efficacy: Doses above 1.2 mg/kg/day in children or 80-100 mg/day in adults show no additional benefit 1, 4