What are the recommended atomoxetine dosing guidelines for children 6‑12 years old, adolescents 13 years and older, adults, and how should the dose be adjusted in moderate or severe hepatic impairment?

Atomoxetine Dosing Guidelines

Children 6–12 Years Old

Start atomoxetine at approximately 0.5 mg/kg/day as a single morning dose or divided into two equal doses (morning and late afternoon/early evening), then increase after a minimum of 3 days to a target total daily dose of approximately 1.2 mg/kg/day. 1, 2

• The maximum recommended total daily dose in children weighing less than 70 kg is 1.4 mg/kg/day or 100 mg, whichever is less 1, 3
• Doses above 1.2 mg/kg/day have not been shown to provide additional benefit but may increase adverse effects 1
• Atomoxetine requires 6–12 weeks to achieve full therapeutic effect, significantly longer than stimulants which work within days 4, 2

Adolescents 13 Years and Older

Initiate atomoxetine at approximately 0.5 mg/kg/day and increase after a minimum of 3 days to a target total daily dose of approximately 1.2 mg/kg/day, administered as a single daily dose in the morning or as evenly divided doses in the morning and late afternoon/early evening. 1, 3

• For adolescents and children weighing more than 70 kg, start at 40 mg/day and increase after a minimum of 3 days to a target dose of 80 mg/day 4
• The maximum recommended dose is 100 mg/day 4, 1
• After 2–4 additional weeks, the dose may be increased to a maximum of 100 mg in patients who have not achieved an optimal response 1, 3

Adults

Begin atomoxetine at 40 mg orally daily, titrate every 7–14 days to 60 mg, then 80 mg daily as tolerated. 4

• The target dose for adults is 60–100 mg daily 4, 2
• The maximum dose is the lesser of 1.4 mg/kg/day or 100 mg/day, whichever is lower 4, 1
• Atomoxetine can be administered as a single morning dose or split into morning and evening doses to reduce adverse effects; evening-only dosing is also an option if needed 4

Dose Adjustments in Hepatic Impairment

In patients with moderate hepatic impairment (Child-Pugh Class B), reduce the initial and target doses to 50% of the normal dose. 5

In patients with severe hepatic impairment (Child-Pugh Class C), reduce the initial and target doses to 25% of the normal dose. 5

• Hepatic insufficiency increases atomoxetine exposure due to reduced metabolism 1
• These reductions apply to all age groups and should be implemented from treatment initiation 5

Critical Monitoring Requirements

• Measure blood pressure and pulse at baseline and regularly during treatment, as atomoxetine causes statistically (but not clinically) significant increases in both parameters 4, 1
• Monitor height and weight at each visit, particularly in younger patients, though initial losses in expected height and weight eventually return to normal in the longer term 4, 1
• Screen for suicidality and clinical worsening at every visit, especially during the first few months or at dose changes, as atomoxetine carries an FDA black box warning for increased suicidal ideation in children and adolescents 4, 2
• Track sleep quality and appetite changes as common adverse effects 4

Special Populations and Considerations

• Atomoxetine is particularly useful for patients at risk of substance abuse, those with comorbid anxiety or tics, or those who do not wish to take a controlled substance 1, 6
• Patients who are poor CYP2D6 metabolizers (approximately 7% of Caucasians) have greater exposure to and slower elimination of atomoxetine; these patients may require lower doses 1, 2
• CYP2D6 inhibitors such as paroxetine produce changes in atomoxetine pharmacokinetics similar to those in poor metabolizers and may necessitate dose adjustment 1, 2
• Atomoxetine has medium-range effect sizes of approximately 0.7 compared to stimulants and is significantly less effective than extended-release methylphenidate formulations and extended-release mixed amphetamine salts 4, 1