Maximum Dosage for Atomoxetine
The maximum recommended total daily dose of atomoxetine is 100 mg/day for all patients, or 1.4 mg/kg/day in children and adolescents, whichever is less. 1
Weight-Based Maximum Dosing
Children and Adolescents ≤70 kg
- Maximum dose: 1.4 mg/kg/day or 100 mg/day, whichever is less 2, 1
- Target therapeutic dose is 1.2 mg/kg/day, with no additional benefit demonstrated at higher doses 1
- The 1.2 mg/kg/day target dose has been shown to reduce ADHD symptoms by 34-38% versus 13-15.7% with placebo 2
Children and Adolescents >70 kg and Adults
- Maximum dose: 100 mg/day 3, 1
- Initial dosing starts at 40 mg/day, increases to target of 80 mg/day after minimum 3 days, then may increase to maximum 100 mg after 2-4 additional weeks if optimal response not achieved 1
- No data support increased effectiveness at doses higher than 100 mg 1
Critical Safety Ceiling
The safety of single doses over 120 mg and total daily doses above 150 mg have not been systematically evaluated 1, making these doses unsafe and not recommended under any circumstances.
Special Population Adjustments to Maximum Dose
Hepatic Impairment
- Moderate hepatic impairment (Child-Pugh Class B): Maximum dose reduced to 50% of normal (50 mg/day for adults, or 0.7 mg/kg/day for children) 1
- Severe hepatic impairment (Child-Pugh Class C): Maximum dose reduced to 25% of normal (25 mg/day for adults, or 0.35 mg/kg/day for children) 1
CYP2D6 Poor Metabolizers or Strong CYP2D6 Inhibitor Use
- Approximately 7% of the population are poor metabolizers via CYP2D6, resulting in significantly higher plasma levels and longer half-lives 3
- When using strong CYP2D6 inhibitors (paroxetine, fluoxetine, quinidine) or in known poor metabolizers, the usual target dose of 1.2 mg/kg/day (children ≤70 kg) or 80 mg/day (>70 kg and adults) should only be reached if symptoms fail to improve after 4 weeks and initial dose is well tolerated 1
- Concomitant SSRIs can elevate serum atomoxetine levels, requiring dose adjustments 3
Important Dosing Pitfalls
- Do not exceed 1.4 mg/kg/day or 100 mg/day in any patient without hepatic impairment or CYP2D6 considerations 2, 3, 1
- Research trials using 1.8 mg/kg/day showed no additional benefit over 1.2 mg/kg/day 4, reinforcing that higher doses provide no therapeutic advantage
- Rapid dose escalation increases risk of behavioral activation, agitation, motor restlessness, insomnia, and aggression, particularly in younger patients 2