What is the recommended starting dose for initiating atomoxetine (Strattera) therapy?

Atomoxetine Initial Dosing Recommendations

For children and adolescents up to 70 kg, atomoxetine should be initiated at 0.5 mg/kg/day, while adults and children over 70 kg should start at 40 mg daily. 1, 2

Detailed Dosing Guidelines

Initial Dosing

• Children and adolescents ≤70 kg: 0.5 mg/kg/day 1, 2
• Adults and children >70 kg: 40 mg daily 1, 2

Titration Schedule

• Increase dose after a minimum of 3 days 2
• Target doses:
  • Children and adolescents ≤70 kg: 1.2 mg/kg/day 1, 2
  • Adults and children >70 kg: 80 mg daily 1, 2

Maximum Doses

• Children and adolescents ≤70 kg: 1.4 mg/kg/day or 100 mg daily (whichever is less) 1, 2
• Adults and children >70 kg: 100 mg daily 1, 2

Administration Considerations

• Can be administered as a single daily dose in the morning or divided into two doses (morning and late afternoon/early evening) 2
• May be taken with or without food 2
• Capsules should be swallowed whole, not opened 2

Special Populations

Hepatic Impairment

• Moderate impairment (Child-Pugh Class B): Reduce initial and target doses to 50% of normal dose 1, 2
• Severe impairment (Child-Pugh Class C): Reduce initial and target doses to 25% of normal dose 1, 2

CYP2D6 Poor Metabolizers or Patients Taking CYP2D6 Inhibitors

• Children and adolescents ≤70 kg: Start at 0.5 mg/kg/day; increase to 1.2 mg/kg/day only if symptoms don't improve after 4 weeks and initial dose is well tolerated 2
• Adults and children >70 kg: Start at 40 mg/day; increase to 80 mg/day only if symptoms don't improve after 4 weeks and initial dose is well tolerated 2

Monitoring and Follow-up

• Monitor for common side effects, particularly:
  • Gastrointestinal effects (most common adverse event) 1, 3
  • Suicidal ideation, especially during first months of treatment 1
  • Blood pressure and heart rate changes 1
  • Hepatic function 1

Efficacy Considerations

• No additional benefit has been demonstrated for doses higher than 1.2 mg/kg/day 2
• Atomoxetine shows a graded dose-response, with 1.2 mg/kg/day appearing to be as effective as 1.8 mg/kg/day for most patients 4
• Lower maintenance doses (0.5 mg/kg/day) may be effective for long-term treatment after initial response to higher doses 5

Clinical Pearls

• Atomoxetine is not a controlled substance and has negligible risk of abuse 6
• Full therapeutic effect may take several weeks to develop, unlike stimulants which work more rapidly
• Screen for bipolar disorder before initiating treatment 2
• Approximately 7% of the population are poor CYP2D6 metabolizers who may require lower doses 1

Remember that atomoxetine is indicated as part of a comprehensive treatment program that may include psychological, educational, and social interventions 2.