Atomoxetine Dose Increase Protocol
For children and adolescents ≤70 kg: start at 0.5 mg/kg/day and increase after a minimum of 3 days to the target dose of 1.2 mg/kg/day; for those >70 kg and adults: start at 40 mg/day and increase after a minimum of 3 days to 80 mg/day, with potential further increase to 100 mg after 2-4 additional weeks if response is inadequate. 1
Weight-Based Dosing Algorithm
Children and Adolescents ≤70 kg:
- Initial dose: 0.5 mg/kg/day
- Timing of increase: After minimum 3 days
- Target dose: 1.2 mg/kg/day (reached by day 4)
- Maximum dose: 1.4 mg/kg/day or 100 mg/day, whichever is less
- Administration: Either once daily in morning OR divided into morning and late afternoon/evening doses 1
Children and Adolescents >70 kg and Adults:
- Initial dose: 40 mg/day
- First increase: After minimum 3 days → 80 mg/day
- Second increase (if needed): After 2-4 additional weeks → 100 mg/day maximum
- Administration: Once daily in morning OR divided doses 1
Critical Monitoring Points
During the first 2 weeks and at each dose change, closely monitor for:
- Suicidal ideation, clinical worsening, and unusual behavioral changes (particularly in children/adolescents) 2
- Early adverse events: decreased appetite, somnolence, nausea, vomiting, fatigue, abdominal pain 2
Evidence-Based Titration Strategy
The FDA-approved "fast titration" (3-day interval) is standard 1, but research suggests slower titration with twice-daily dosing may reduce early adverse events. One comparative study found that titrating to 1.2 mg/kg/day over 2 weeks with twice-daily dosing resulted in lower rates of decreased appetite (8.0% vs 14.3%) and somnolence (4.2% vs 14.3%) compared to fast/once-daily titration 3. However, completion rates were similar between approaches 3.
Clinical pearl: If tolerability is a concern, consider twice-daily dosing with gradual weekly increases over the first 2 weeks, though this is slower than FDA labeling.
When to Increase Beyond Target Dose
After reaching the target dose (1.2 mg/kg/day or 80 mg/day):
- Wait 2-4 weeks to assess response 1
- If symptoms have not achieved optimal improvement AND the current dose is well-tolerated, increase to maximum (1.4 mg/kg/day or 100 mg/day)
- Important caveat: No data support increased effectiveness at doses higher than 1.2 mg/kg/day in children 1, 4
Special Dosing Adjustments
CYP2D6 Poor Metabolizers or Strong Inhibitor Use:
When patients are taking strong CYP2D6 inhibitors (paroxetine, fluoxetine, quinidine) or are known poor metabolizers:
For ≤70 kg:
- Start: 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
For >70 kg and adults:
- Start: 40 mg/day
- Increase to 80 mg/day only if symptoms fail to improve after 4 weeks AND initial dose is well-tolerated 1
Hepatic Impairment:
- Moderate (Child-Pugh B): Reduce initial and target doses to 50% of normal
- Severe (Child-Pugh C): Reduce initial and target doses to 25% of normal 1
Common Pitfalls to Avoid
Increasing too rapidly in CYP2D6 poor metabolizers - These patients (approximately 7% of population) have significantly higher plasma levels and longer half-lives, increasing adverse effect risk 2
Exceeding 1.2 mg/kg/day expecting better efficacy - Research shows no additional benefit at higher doses in children 1, 4
Failing to screen for bipolar disorder before initiation - Required screening per FDA labeling 1
Not monitoring cardiovascular parameters - Contraindicated in severe cardiovascular disorders and pheochromocytoma 1
Inadequate monitoring during dose changes - Suicidality risk is specifically elevated during initial treatment and dose adjustments in youth 2
Maintenance Considerations
Once optimal response is achieved, periodically reevaluate the long-term need for continued treatment 1. The medication can be discontinued without tapering 1. Controlled trial data support maintenance efficacy in the 1.2-1.8 mg/kg/day range for pediatric patients 1.