What is the recommended dosing schedule for atomoxetine (Strattera) in children (≥6 years), adolescents, and adults, and how should the dose be adjusted for hepatic or renal impairment?

Strattera (Atomoxetine) Dosing

For children and adolescents ≤70 kg, start atomoxetine at 0.5 mg/kg/day and increase after a minimum of 3 days to a target dose of 1.2 mg/kg/day (maximum 1.4 mg/kg or 100 mg, whichever is less); for children/adolescents >70 kg and adults, start at 40 mg/day and increase after 3 days to a target of 80 mg/day (maximum 100 mg/day). 1

Standard Dosing by Weight

Children and Adolescents ≤70 kg (≥6 years)

• Initial dose: 0.5 mg/kg/day
• Target dose: 1.2 mg/kg/day (after minimum 3 days)
• Maximum dose: 1.4 mg/kg/day OR 100 mg/day, whichever is less
• After 2-4 additional weeks at target, may increase to maximum if response is suboptimal 1

Children/Adolescents >70 kg and Adults

• Initial dose: 40 mg/day
• Target dose: 80 mg/day (after minimum 3 days)
• Maximum dose: 100 mg/day
• After 2-4 additional weeks at target, may increase to 100 mg if response inadequate 1

Administration Details

• Can be given as single morning dose OR divided into morning and late afternoon/evening doses 1
• May take with or without food 1
• Capsules must be swallowed whole, not opened 1
• Can be discontinued without tapering 1

Dose Adjustments for Special Populations

Hepatic Impairment

Moderate hepatic impairment (Child-Pugh Class B):

• Reduce initial and target doses to 50% of normal dose 1, 2

Severe hepatic impairment (Child-Pugh Class C):

• Reduce initial and target doses to 25% of normal dose 1, 2

The rationale: Hepatic impairment significantly reduces atomoxetine clearance due to decreased CYP2D6 activity and hepatic blood flow, resulting in 1.9-fold increased exposure 2.

CYP2D6 Poor Metabolizers or Strong CYP2D6 Inhibitor Use

Children/adolescents ≤70 kg:

• Start at 0.5 mg/kg/day
• Only increase to usual target of 1.2 mg/kg/day if symptoms fail to improve after 4 weeks AND initial dose is well tolerated 1

Children/adolescents >70 kg and adults:

• Start at 40 mg/day
• Only increase to usual target of 80 mg/day if symptoms fail to improve after 4 weeks AND initial dose is well tolerated 1

Strong CYP2D6 inhibitors include paroxetine, fluoxetine, and quinidine 1.

Renal Impairment

No specific dosage adjustment is provided in the FDA labeling for renal impairment 1.

Critical Timing Considerations

Allow adequate time for response assessment: The trajectory of atomoxetine response is incremental over weeks to months, not days 3. Many patients continue improving for up to 24 weeks 3. Assess efficacy only after 4-6 weeks at target dose before concluding treatment failure 4, 3.

This is a common pitfall—real-world data show clinicians frequently underdose atomoxetine (averaging ~60 mg/day in adults vs. the 80 mg target), likely due to premature efficacy judgments 4.

Safety Monitoring

Before initiating treatment, obtain personal and family cardiac history 5. If risk factors present, perform ECG and consider cardiology referral 5. Monitor for:

• Suicidal ideation (FDA black box warning): Increased risk in children/adolescents, particularly early in treatment 5, 1
• Blood pressure and heart rate changes: Can cause increases; use caution in hypertension or cardiovascular disease 5, 1
• Hepatotoxicity: Extremely rare but discontinue if jaundice or liver injury occurs 5, 1
• Growth parameters: Monitor height/weight in pediatric patients 5, 1

Contraindications

Absolute contraindications include 1:

• Use within 2 weeks of MAOI
• Narrow-angle glaucoma
• Pheochromocytoma or history thereof
• Severe cardiovascular disorders that would deteriorate with clinically important BP/HR increases
• Hypersensitivity to atomoxetine

Maintenance Treatment

Maintenance dosing continues at the same dose used to achieve response (typically 1.2-1.8 mg/kg/day in pediatric patients) 1. Periodically reassess long-term need, though atomoxetine has demonstrated sustained efficacy and notably, 50% of adults maintain response for at least 6 months after discontinuation following 6 months of treatment 3.