How long does Strattera (atomoxetine) take to start working?

Strattera (Atomoxetine) Time to Start Working

Atomoxetine requires 6-12 weeks to achieve full therapeutic effect, which is substantially longer than stimulant medications that work within 30 minutes to 2 hours. 1, 2

Timeline of Therapeutic Response

Initial improvements may be observed within 2 weeks of treatment initiation, but clinically significant improvement typically occurs by week 6, with maximal therapeutic benefit not reached until week 12 or later. 1 This delayed onset is fundamentally different from stimulant medications (methylphenidate, dextroamphetamine) which begin working within 30 minutes after ingestion and produce effects lasting 3-4 hours. 3

Key Timing Considerations:

• Early response (2 weeks): Some patients may notice statistically significant but not yet clinically meaningful improvements 1
• Clinically significant response (6 weeks): Most patients who will respond begin showing meaningful symptom reduction 1
• Maximal response (12+ weeks): Full therapeutic benefit requires at least 3 months of continuous treatment 1, 2

Clinical Implications for Treatment Planning

Patients and families must be counseled about this delayed onset to prevent premature discontinuation. 1 This is particularly important because:

• The smaller effect size of atomoxetine (0.7) compared to stimulants (1.0) means the benefits may be less dramatic even when fully established 2
• Common side effects (decreased appetite, nausea, headache, initial somnolence) often emerge within the first few weeks of treatment, potentially before therapeutic benefits are apparent 1, 2
• Assessment of treatment response should not occur before 6-12 weeks, as earlier evaluation may incorrectly suggest treatment failure 1, 2

Dosing Strategy to Optimize Response

Atomoxetine should be initiated at 0.5 mg/kg/day and titrated after a minimum of 3 days to a target dose of 1.2 mg/kg/day (maximum 1.4 mg/kg/day or 100 mg/day, whichever is lower). 4 The medication can be administered as a single daily dose or split into two divided doses to reduce gastrointestinal side effects. 2, 4

Important Dosing Adjustments:

• With CYP2D6 inhibitors or poor metabolizers: Initiate at 0.5 mg/kg/day and only increase to 1.2 mg/kg/day after 4 weeks if symptoms fail to improve and the initial dose is well tolerated 4
• Split dosing strategy: Dividing the dose may reduce gastrointestinal side effects, particularly if dosage is increased too rapidly 2

Monitoring During the Onset Period

During the 6-12 week onset period, monitor blood pressure and heart rate regularly, as atomoxetine can increase both parameters. 2 Additionally:

• Screen for suicidal ideation especially during the first few months of treatment or with dose changes, given the FDA black box warning for increased risk in children and adolescents 1, 2
• Assess for common adverse effects including decreased appetite, nausea, vomiting, headache, somnolence, and abdominal pain 1, 2
• Avoid premature dose escalation beyond the target of 1.2 mg/kg/day during the initial weeks, as higher doses have not demonstrated additional benefit 4

Comparison to Alternative Treatments

If rapid symptom control is needed, stimulant medications (methylphenidate or amphetamine derivatives) should be considered as first-line therapy, as they produce effects within 30 minutes to 2 hours. 3, 1 Atomoxetine is positioned as second-line therapy due to its smaller effect size and delayed onset, but may be preferred as first-line in specific situations:

• Patients with comorbid or at-risk substance use disorders 2
• Patients with Tourette's syndrome or tics 2
• Patients requiring around-the-clock symptom control without stimulant peaks and valleys 1, 2
• Patients experiencing sleep problems on stimulants, particularly those with autism spectrum disorder comorbidity 2

Common Pitfall to Avoid

The most critical error is discontinuing atomoxetine before 6-12 weeks due to perceived lack of efficacy. 1, 2 Patients and families must understand that unlike stimulants which work immediately, atomoxetine's mechanism as a selective norepinephrine reuptake inhibitor requires time to produce sustained neurochemical changes that reduce ADHD symptoms. 5, 6 Premature discontinuation during the onset period prevents assessment of true treatment response and may lead to unnecessary medication switches.