From the FDA Drug Label
- 4 Switching Patients from WELLBUTRIN Tablets (Bupropion Hydrochloride Tablets) or from WELLBUTRIN SR Sustained-Release Tablets (Bupropion Hydrochloride Sustained-Release Tablets (SR))
When switching patients from WELLBUTRIN tablets (bupropion hydrochloride tablets) to bupropion hydrochloride extended-release tablets (XL) or from WELLBUTRIN SR sustained-release tablets (bupropion hydrochloride sustained-release tablets (SR)) to bupropion hydrochloride extended-release tablets (XL), give the same total daily dose when possible.
The difference between Wellbutrin (bupropion) SR and Wellbutrin (bupropion) HCL is the release formulation.
- Wellbutrin SR is a sustained-release formulation, which releases the medication slowly over time.
- Wellbutrin HCL is an immediate-release formulation, which releases the medication quickly.
To switch from HCL to SR, you can give the same total daily dose when possible. However, the exact switching schedule is not specified in the label. It is recommended to consult a healthcare professional for specific guidance on switching between these formulations 1.
From the Research
Wellbutrin SR and Wellbutrin HCL are both formulations of bupropion, but they differ in their release mechanisms, with SR releasing the medication gradually over 12 hours and HCL releasing it more quickly. When considering the switch from Wellbutrin HCL to SR, it's essential to understand that both formulations are bioequivalent in terms of systemic exposure to bupropion 2, 3. The main difference lies in their dosing schedules: Wellbutrin SR is taken twice daily, while Wellbutrin HCL is taken three times daily.
Key Points to Consider:
- The total daily dose may remain similar when switching from HCL to SR, but the SR formulation will be given in fewer, larger doses.
- For example, if you were taking 100 mg of Wellbutrin HCL three times daily (300 mg total), you might switch to 150 mg of Wellbutrin SR twice daily.
- This transition should always be supervised by your healthcare provider to monitor for any side effects or changes in effectiveness.
- The sustained-release formulation was developed to improve medication adherence and reduce side effects by avoiding peaks and valleys in blood concentration that can occur with immediate-release formulations.
- A recent study in 2019 confirmed the bioequivalence and therapeutic equivalence of generic and brand bupropion, including the SR formulation, providing reassurance about the consistency of these medications 4.
- Additionally, a systematic review and meta-analysis from 2016 supported the effectiveness of bupropion as an antidepressant, highlighting its unique pharmacology and potential benefits, such as low rates of sexual dysfunction and weight loss rather than gain 5.
Recommendations:
- Switching from Wellbutrin HCL to SR should be done under medical supervision, adjusting the dosing schedule from three times daily to twice daily, with the total daily dose potentially remaining similar but in fewer, larger doses.
- It's crucial to follow the guidance of a healthcare provider to ensure a safe and effective transition between formulations.
- Patients should not adjust their medication schedule or dosage without consulting their doctor first, as improper transitions could affect treatment efficacy or cause unwanted side effects.