Atomoxetine Dosing After Initial Trial
For a 74 lb (33.6 kg) child who has already completed the initial low-dose trial of atomoxetine, increase to the target dose of approximately 1.2 mg/kg/day (approximately 40 mg daily), administered either as a single morning dose or divided into morning and late afternoon/evening doses 1.
Dosing Algorithm
Since this child weighs 74 lb (33.6 kg), which is under 70 kg, follow the pediatric weight-based dosing protocol:
- Target dose: 1.2 mg/kg/day = approximately 40 mg/day total
- Maximum dose: Do not exceed 1.4 mg/kg/day (47 mg/day) or 100 mg/day, whichever is less 1
- Dosing schedule: Can give once daily in the morning OR split into two doses (morning and late afternoon/evening) 1
The FDA labeling is explicit that after the minimum 3-day initial period at 0.5 mg/kg/day, you should increase to the target of 1.2 mg/kg/day 1. No additional benefit has been demonstrated for doses higher than 1.2 mg/kg/day 1.
Key Evidence Supporting This Recommendation
The dose-response study by Michelson et al. demonstrated that 1.2 mg/kg/day and 1.8 mg/kg/day were equally effective and superior to both placebo and 0.5 mg/kg/day, with no additional benefit at the higher dose 2. This establishes 1.2 mg/kg/day as the appropriate target for most patients.
While one maintenance study suggested that some patients who respond acutely can be maintained on lower doses (0.5 mg/kg/day) 3, this applies only to patients who have already achieved robust response and are being considered for dose reduction during long-term maintenance—not for patients still in the acute treatment phase.
Important Caveats
Monitor for these adverse effects as you uptitrate 4:
- Initial somnolence and GI symptoms (particularly if dose increased too rapidly)
- Decreased appetite
- Increased heart rate and blood pressure (mild increases expected)
- Rarely: increased suicidal thoughts (FDA black box warning)
Ensure cardiac screening was completed before starting atomoxetine, including personal and family history of sudden death, cardiovascular symptoms, and specific cardiac conditions 4.
The medication can be taken with or without food and should be swallowed whole, not opened 1.