Dose Conversion from Wellbutrin SR to Wellbutrin XL
When converting from Wellbutrin SR (sustained release) to Wellbutrin XL (extended release), use the same total daily dose, as both formulations are bioequivalent in terms of systemic exposure to bupropion. 1
Conversion Guidelines
Direct Conversion Approach
- Wellbutrin SR is typically administered twice daily
- Wellbutrin XL is administered once daily in the morning
- When switching from SR to XL:
- 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 (though 200 mg XL is not a standard dose, so 150 mg XL may be used)
- 150 mg SR once daily → 150 mg XL once daily
Administration Considerations
- Wellbutrin XL should be swallowed whole and not crushed, divided, or chewed 1
- Administer Wellbutrin XL in the morning with or without food 1
- Unlike SR formulation which requires twice-daily dosing, XL provides the convenience of once-daily administration 2
Dosing Adjustments for Special Populations
Hepatic Impairment
- For moderate to severe hepatic impairment (Child-Pugh score 7-15): Maximum XL dose is 150 mg every other day 1
- For mild hepatic impairment (Child-Pugh score 5-6): Consider reducing the dose and/or frequency 1
Renal Impairment
- Consider reducing the dose and/or frequency in patients with renal impairment (GFR <90 mL/min) 1
Pharmacokinetic Considerations
- All three formulations of bupropion (IR, SR, and XL) are bioequivalent in terms of systemic exposure to bupropion 2, 3
- Absorption profile differences:
- IR: Tmax approximately 1.5 hours
- SR: Tmax approximately 3 hours
- XL: Tmax approximately 5 hours 3
- The extended absorption profile of XL allows for once-daily dosing while maintaining therapeutic levels 3
Discontinuation Protocol
If discontinuing Wellbutrin XL treatment at a dose of 300 mg once daily, decrease to 150 mg once daily for 1-2 weeks prior to complete discontinuation to minimize withdrawal symptoms 1, 4
Clinical Considerations
- The conversion maintains therapeutic efficacy while potentially improving adherence through simplified dosing 2, 5
- Monitor for common side effects which may include insomnia, dry mouth, anxiety/jitteriness, decreased appetite, and headache 4
- Regular monitoring of blood pressure and heart rate is necessary, especially during the first 12 weeks of treatment 4
This straightforward conversion from Wellbutrin SR to XL maintains the same total daily dose while offering the convenience of once-daily administration, which may improve medication adherence for patients.