Cross-Taper from Strattera 40 mg to Wellbutrin XL 150 mg
Do not perform a cross-taper between atomoxetine (Strattera) 40 mg and bupropion XL (Wellbutrin XL) 150 mg—instead, taper off atomoxetine completely over 1-2 weeks, then start bupropion XL 150 mg after discontinuation.
Rationale for Sequential Switch (Not Cross-Taper)
A true cross-taper is contraindicated here due to a significant pharmacokinetic drug-drug interaction. Bupropion is a potent CYP2D6 inhibitor that increases atomoxetine exposure by 5.1-fold 1. When these medications are combined, atomoxetine plasma concentrations (AUC) increase dramatically from 1580 to 8060 ng*h/mL, while its active metabolite decreases 1.5-fold 1. This creates substantial risk for atomoxetine toxicity including cardiovascular adverse events (hypertension, tachycardia, syncope) 2.
Recommended Switching Protocol
Step 1: Taper Atomoxetine
- Week 1: Reduce atomoxetine from 40 mg to 20 mg daily
- Week 2: Reduce to 10 mg daily (or discontinue after week 1 if well-tolerated)
- After Week 2: Complete discontinuation
Atomoxetine does not require extended tapering at this low dose (40 mg), but gradual reduction over 1-2 weeks minimizes potential withdrawal symptoms and allows monitoring for symptom exacerbation 3.
Step 2: Washout Period
- Wait 3-5 days after final atomoxetine dose before starting bupropion
- This allows clearance of atomoxetine (half-life ~5 hours in extensive metabolizers, longer in poor metabolizers) 4
Step 3: Initiate Bupropion XL
- Start at 150 mg once daily in the morning (taken whole, not crushed) 5
- If tolerated and clinically indicated, may increase to 300 mg daily after minimum 4 days (though full antidepressant effect may take 4+ weeks) 5
- Maximum dose: 450 mg/day as single dose 5
Critical Safety Considerations
Seizure Risk with Bupropion
Bupropion lowers seizure threshold and is contraindicated in patients with seizure disorders or conditions that increase seizure risk 6, 7. The incidence is dose-dependent (approximately 1:1500 at therapeutic doses) 6. Gradual dose escalation is essential to minimize this risk 5.
Cardiovascular Monitoring
Both medications affect cardiovascular parameters:
- Atomoxetine: Can increase heart rate and blood pressure 8
- Bupropion: Associated with tachycardia (ROR 4.2) and hypertension (ROR 3.5) 2
Monitor blood pressure and heart rate at baseline, during the taper, and after starting bupropion.
Neuropsychiatric Effects
Both medications carry warnings for neuropsychiatric adverse events including depression, suicidal ideation, and behavioral changes 7, 8. Monitor closely during the transition period, especially in the first 4-8 weeks after starting bupropion 7.
Common Pitfalls to Avoid
- Do not overlap these medications due to the CYP2D6 interaction risk 1
- Do not crush or split Wellbutrin XL tablets—this increases seizure risk 5
- Do not abruptly discontinue atomoxetine at higher doses without tapering, though 40 mg is relatively low
- Avoid bedtime dosing of bupropion—give in the morning to minimize insomnia 5
- Do not use bupropion in patients with eating disorders, alcohol withdrawal, or concurrent MAO inhibitor use 6, 7
Expected Timeline and Efficacy
- Atomoxetine discontinuation symptoms: Typically minimal at 40 mg dose, resolve within days
- Bupropion onset for ADHD: Less efficacious than stimulants for ADHD 4, but may provide benefit for comorbid depression
- Full therapeutic effect: May require 4+ weeks at target dose 5
Special Populations
Hepatic impairment: Reduce bupropion XL to 150 mg every other day in severe cirrhosis; use caution and reduced frequency in mild-moderate impairment 5
Renal impairment: Use bupropion with caution and consider reduced frequency/dose 5
Pregnancy/breastfeeding: Bupropion has more safety data than atomoxetine in pregnancy, though small increases in specific cardiac malformations have been reported 4. For breastfeeding, bupropion is present in milk with rare case reports of infant seizures 4.