What is the recommended approach when switching from Wellbutrin (bupropion) SR to XL?

Switching from Wellbutrin SR to XL

When switching from Wellbutrin SR (sustained-release) to XL (extended-release), maintain the same total daily dose while changing from twice-daily to once-daily morning administration. 1, 2

Dosing Conversion Protocol

The conversion process should follow these steps:

1. Determine current total daily dose of Wellbutrin SR

   • SR is typically taken twice daily (100-150 mg BID) 1
   • Calculate the sum of both daily doses

2. Convert to equivalent XL dose

   • Administer the same total daily dose as a single morning dose 2
   • For example:
     • 150 mg SR twice daily (300 mg total) → 300 mg XL once daily
     • 100 mg SR twice daily (200 mg total) → 200 mg XL once daily (or nearest available dose)

3. Timing of administration

   • Take XL formulation once daily in the morning 2
   • Do not take late in the day to minimize risk of insomnia 1

Important Clinical Considerations

• Bioequivalence: All three formulations (IR, SR, and XL) are bioequivalent in terms of systemic exposure to bupropion 3

• Pharmacokinetic differences:

  • XL provides more consistent plasma levels over 24 hours 4
  • XL has lower maximum concentration (Cmax) and longer time to maximum concentration compared to SR 4

• Advantages of XL formulation:

  • Improved adherence with once-daily dosing 3
  • Potentially fewer side effects due to smoother plasma levels 3
  • May reduce insomnia compared to twice-daily dosing 5

• Swallowing instructions:

  • XL tablets must be swallowed whole
  • Do not crush, divide, or chew the tablets 2

Monitoring After Switching

• Efficacy: Assess therapeutic response after 1-2 weeks

  • Once-daily dosing appears to be at least as effective as twice-daily dosing 5

• Side effects: Monitor for:

  • Insomnia (take dose in morning only) 2
  • Headache, dry mouth, nausea 1
  • Rare but serious: seizures, dystonic reactions 6

Special Populations

• Hepatic impairment:

  • Moderate to severe impairment: Maximum 150 mg every other day
  • Mild impairment: Consider reducing dose/frequency 2

• Renal impairment:

  • Consider reducing dose/frequency in patients with GFR <90 mL/min 2

Common Pitfalls to Avoid

• Abrupt discontinuation: When discontinuing treatment with bupropion XL 300 mg daily, decrease to 150 mg once daily prior to full discontinuation 2

• Seizure risk: Increase dose gradually to minimize seizure risk 2

• Drug interactions:

  • Allow at least 14 days between discontinuing MAOIs and starting bupropion 2
  • Similarly, wait 14 days after stopping bupropion before starting an MAOI 2

• Timing errors: Taking XL formulation late in the day can increase insomnia risk 1