Recommended Atomoxetine Initiation Dose
Start atomoxetine at 40 mg once daily for this 19-year-old patient, as this is the standard initial dose for adults and adolescents weighing over approximately 70 kg. 1
Initial Dosing Strategy
- The recommended starting dose is 40 mg once daily, taken in the morning or evening 1
- After a minimum of 3 days at the initial dose, increase to the target therapeutic dose of 80 mg daily if tolerated 1
- The dose can be administered either as a single daily dose or split into two evenly divided doses (morning and late afternoon/early evening) 2, 3
Titration Schedule
- Adjust the dose every 7-14 days based on response and tolerability 1
- The target maintenance dose is typically 80-100 mg daily 1
- Maximum recommended dose is the lesser of 1.4 mg/kg/day or 100 mg/day 1
Critical Drug Interaction Considerations
Bupropion is a moderate CYP2D6 inhibitor, which will significantly elevate atomoxetine serum levels. 1 This interaction requires careful attention:
- Atomoxetine is primarily metabolized through the CYP2D6 pathway 1
- Bupropion inhibits CYP2D6, potentially causing atomoxetine levels to increase 2-4 fold 1
- Approximately 7% of the population are poor CYP2D6 metabolizers naturally, experiencing significantly higher plasma levels and longer half-lives 1
- Start with the standard 40 mg dose but monitor closely for adverse effects, as this patient will effectively function as a "poor metabolizer" due to the bupropion interaction 1
- Consider slower titration intervals (every 2-3 weeks rather than weekly) given this interaction
Monitoring Requirements for This Specific Patient
Close monitoring for suicidal ideation is mandatory, particularly during the first few months of treatment: 1
- This patient has depression, anxiety, and ADHD—a high-risk combination
- She is 19 years old, within the age range (<24 years) requiring heightened suicide risk monitoring 4
- Atomoxetine carries a black box warning for increased suicidal ideation in children and adolescents 1
- Monitor closely for suicidality, clinical worsening, and unusual behavioral changes, especially during the first few months and at times of dose changes 1
Cardiovascular monitoring is essential: 1
- Measure blood pressure and pulse at baseline and regularly during treatment 1
- Both bupropion and atomoxetine can increase blood pressure and heart rate 1, 4
- The combination may have additive cardiovascular effects requiring closer monitoring
Common Adverse Effects to Anticipate
The most common adverse effects in adults include: 1, 2
- Dry mouth, insomnia, nausea, decreased appetite 1, 2
- Constipation, dizziness, sweating, dysuria 2
- Sexual problems and palpitations 2
- These effects are typically mild to moderate and often transient 5
Bupropion Dose Adjustment Consideration
Regarding the planned increase of bupropion from 150 mg to 200 mg daily:
- Note that Wellbutrin SR does not come in a 200 mg tablet formulation 4
- Standard SR dosing is 150 mg once or twice daily 4
- If increasing the bupropion dose, the appropriate step would be to 150 mg twice daily (300 mg total daily dose), not 200 mg 4
- The second dose of bupropion SR should be given before 3 PM to minimize insomnia risk 4
Clinical Advantages of This Combination
This combination of bupropion and atomoxetine is rational for this patient: 6
- Atomoxetine monotherapy has demonstrated effectiveness for ADHD with comorbid depressive and anxiety symptoms 6
- Bupropion addresses depression through noradrenergic/dopaminergic pathways while atomoxetine provides noradrenergic enhancement for ADHD control 1, 4
- Both medications work through complementary noradrenergic mechanisms without the abuse liability of stimulants 2, 3
- Atomoxetine can be particularly useful for patients with comorbid anxiety, which this patient has 3