Initial Dosage of Atomoxetine (Strattera) for ADHD
The initial dosage of atomoxetine for children and adolescents up to 70 kg is 0.5 mg/kg/day, while for adults and children over 70 kg, the initial dose is 40 mg/day. 1
Dosing Guidelines by Age Group
Children and Adolescents (≤70 kg)
- Starting dose: 0.5 mg/kg/day 2, 1
- Target dose: Increase after a minimum of 3 days to approximately 1.2 mg/kg/day 1
- Maximum dose: 1.4 mg/kg/day or 100 mg/day, whichever is less 2, 1
- Administration: Can be given as a single morning dose or divided into morning and late afternoon doses 1
Adults and Children >70 kg
- Starting dose: 40 mg/day 3, 1
- Target dose: Increase after a minimum of 3 days to approximately 80 mg/day 1
- Maximum dose: 100 mg/day 2, 1
- Administration: Can be given as a single morning dose or divided into morning and late afternoon doses 1
Dosing Adjustments for Special Populations
CYP2D6 Poor Metabolizers or Patients Taking CYP2D6 Inhibitors
- Children and adolescents ≤70 kg: Start at 0.5 mg/kg/day and only increase to the target dose of 1.2 mg/kg/day if symptoms don't improve after 4 weeks 1
- Adults and children >70 kg: Start at 40 mg/day and only increase to the target dose of 80 mg/day if symptoms don't improve after 4 weeks 1
Hepatic Impairment
- Moderate impairment (Child-Pugh Class B): Reduce initial and target doses to 50% of normal dose 1
- Severe impairment (Child-Pugh Class C): Reduce initial and target doses to 25% of normal dose 1
Efficacy and Dose-Response Relationship
Research has demonstrated a graded dose-response relationship with atomoxetine, with 1.2 mg/kg/day showing superior efficacy compared to lower doses 4. Studies have shown that:
- 1.2 mg/kg/day and 1.8 mg/kg/day doses show similar efficacy outcomes, suggesting 1.2 mg/kg/day is the appropriate initial target dose for most patients 4
- No additional benefit has been demonstrated for doses higher than 1.2 mg/kg/day 1
- For maintenance treatment after achieving a robust response, a lower dose of 0.5 mg/kg/day may be effective for some patients 5
Administration Considerations
- Atomoxetine can be taken with or without food 1
- Capsules should be taken whole, not opened 1
- No tapering is required when discontinuing atomoxetine 1
- Dose adjustments should be made at intervals of no less than 3 days 1
Safety Monitoring
- Screen for bipolar disorder prior to starting atomoxetine 1
- Monitor for suicidal ideation, particularly in children and adolescents during the first few months of treatment 2
- Be aware of potential cardiovascular effects including modest increases in heart rate and blood pressure 6
- Common side effects include nausea, vomiting, fatigue, decreased appetite, abdominal pain, and somnolence 2, 6
Clinical Pearls
- Atomoxetine is not a controlled substance and has negligible abuse potential, making it suitable for patients with substance use concerns 7
- Full therapeutic effect may take several weeks to develop, unlike stimulants which often work immediately
- Once-daily dosing is possible and may improve medication adherence 3
- Atomoxetine may be particularly useful for patients with comorbid anxiety or tics 3
Following these dosing guidelines will help optimize the therapeutic benefits of atomoxetine while minimizing potential adverse effects in the treatment of ADHD.