Bupropion SR 150mg BID vs Bupropion XL 150mg Daily
Bupropion SR 150mg twice daily is not equivalent to bupropion XL 150mg once daily; they are significantly different in total daily dose (300mg vs 150mg) and release kinetics, though they share the same active ingredient. 1
Pharmacokinetic Differences
Formulation Characteristics
- Sustained Release (SR): Designed for twice-daily dosing with a median time to peak plasma concentration of approximately 3 hours 1, 2
- Extended Release (XL): Designed for once-daily dosing with a median time to peak plasma concentration of approximately 5 hours 1, 2
Bioequivalence
- Bioequivalence studies have demonstrated that bupropion SR 150mg twice daily (300mg total) is equivalent to bupropion XL 300mg once daily in terms of:
- Peak plasma concentration
- Area under the curve for bupropion
- Area under the curve for the three active metabolites 1
Dosing Comparison
- Bupropion SR 150mg BID provides a total daily dose of 300mg
- Bupropion XL 150mg daily provides only half that amount (150mg total)
- The FDA-approved label clearly indicates these are not equivalent dosages 1
Clinical Implications
Efficacy Considerations
- For major depressive disorder (MDD), the recommended target dose is 300mg daily for both formulations 1
- Starting dose for both formulations is 150mg daily, but titration schedules differ:
- SR: Start with 150mg once daily, increase to 150mg twice daily after 3-4 days
- XL: Start with 150mg once daily, increase to 300mg once daily after 4 days 1
Practical Considerations
- Adherence: Once-daily XL formulation may improve medication adherence compared to twice-daily SR formulation 3
- Timing: SR formulation requires careful timing of second dose (before 3pm) to minimize insomnia risk 4
- Switching between formulations: When switching from SR to XL, the same total daily dose should be maintained when possible 1
Special Populations
Hepatic Impairment
- For moderate to severe hepatic impairment:
- Maximum XL dose is 150mg every other day
- Dose adjustments are required for both formulations 1
Renal Impairment
- Consider reducing dose and/or frequency for patients with renal impairment (GFR <90 mL/min) 1
Common Adverse Effects
Both formulations share similar adverse effect profiles, including:
- Insomnia
- Dry mouth
- Anxiety/jitteriness
- Decreased appetite
- Headache
- Potential for increased blood pressure and heart rate 4
Key Takeaway
When considering therapeutic equivalence, bupropion SR 150mg twice daily (300mg total) would be equivalent to bupropion XL 300mg once daily, not bupropion XL 150mg once daily. The difference in total daily dose (300mg vs 150mg) is clinically significant for efficacy in treating depression and other approved indications 1, 2.