How should I transition an adult from atomoxetine (Strattera) 100 mg to viloxazine (Quelbree)?

Transitioning from Atomoxetine 100 mg to Viloxazine ER in Adults

You can switch directly from atomoxetine 100 mg to viloxazine ER without any washout period, starting viloxazine at 200 mg once daily in the morning. 1

Direct Switch Protocol

No washout period is required because atomoxetine and viloxazine have no overlapping toxicities or dangerous pharmacodynamic interactions, unlike biologic therapies that typically require four drug half-lives of clearance. 1

Starting Dose and Titration

• Begin viloxazine ER at 200 mg once daily on the day after stopping atomoxetine 1
• Administer in the morning for optimal ADHD symptom control throughout the day 2
• Titrate by 200 mg increments at weekly intervals based on response and tolerability 1
• Maximum daily dose is 600 mg/day 1

Expected Timeline for Therapeutic Effect

• Full therapeutic effects may not be evident until 2-4 weeks after initiation, though some benefits may appear by week 2 3, 2
• This delayed onset is important to communicate to patients to prevent premature discontinuation

Mandatory Monitoring During Transition

Cardiovascular Monitoring

Record baseline vital signs before the switch and recheck within 1-2 weeks after starting viloxazine, as both medications can increase blood pressure and heart rate. 1

• Monitor for increased blood pressure and pulse 1
• These cardiovascular effects are generally well tolerated but require documentation 1

Psychiatric Monitoring

Close observation for emergent suicidal thoughts is essential throughout the transition period, as both agents carry warnings for suicidal ideation (particularly through age 24 years). 1

• This risk appears lower with viloxazine than atomoxetine, but vigilance remains necessary 1
• Monitor for behavioral activation, agitation, hypomania, or mania 1

Common Side Effects to Anticipate

The most frequently reported adverse effects with viloxazine include:

• Gastrointestinal symptoms (nausea, vomiting, abdominal discomfort, diarrhea) are most common 1
• Diaphoresis, dry mouth, dizziness, headache, tremor 1
• Insomnia or somnolence (paradoxically, both can occur) 1
• Decreased appetite and weight loss 1
• Fatigue 1

Serious but Uncommon Adverse Effects

• Serotonin syndrome risk, particularly when combined with other serotonergic agents—monitor especially in the first 24-48 hours after starting or dose adjustments 1
• Sexual dysfunction, seizures, abnormal bleeding 1

Key Mechanistic Differences

Viloxazine differs from atomoxetine by having moderate activity at serotonin 5-HT2C receptors in addition to norepinephrine reuptake inhibition, representing a dual mechanism versus atomoxetine's pure norepinephrine reuptake inhibition. 1

• This serotonergic component may contribute to therapeutic effect but also necessitates caution with other serotonergic medications 1

Setting Realistic Expectations

The effect size of viloxazine (approximately 0.7) is similar to atomoxetine and lower than stimulants (approximately 1.0), so patients should not expect dramatically different efficacy. 1

• If the patient had inadequate response to atomoxetine 100 mg, consider whether a stimulant might be more appropriate rather than switching to another nonstimulant with similar efficacy 2
• Stimulants show larger effect sizes for ADHD core symptoms 2

Critical Pitfall to Avoid

Do not discontinue viloxazine abruptly if side effects emerge—work with the patient to determine appropriate dose adjustment or alternative strategies. 3