I was taking Wellbutrin xl for 4 weeks and the doctor changed it for SR and generic. I will like to know the difference and if I shoud change them for the original. Tomorrow is my first day taking Wellbutrin. SR generic is a round big yellow tablet. Please can you help me? I'm afraid is not the same.

Answered by: Jonathan W. Stewart

Wellbutrin XL and Wellbutrin SR are the same chemical, bupropion. This medication is also available without the extra letters as Wellbutrin and generic bupropion (also as Xyban). The differences are in how they get bupropion into the body, and have nothing to do with what bupropion does inside the brain. We might call Wellbutrin, Zyban adn generic bupropion "immediate release" bupropion, Wellbutrin SR "intermediate release" bupropion and Wellbutrin XL "extended release" bupropion.

Thus, the immediate release formulation is mostly absorbed in a few hours, the delay in release of intermediate release bupropion is more like 5-6 hours and extended release bupropion takes closer to 8 hours to get into the body. Because the same amount is getting into the body over a longer time, the longer release formulations ought to produce fewer side effects, but I am not aware of that having been demonstrated.

The most practical difference is that at maximal doses, the immediate release formulation is marketed as a three times daily dosing, while the intermediate release is dosed twice daily and the extended release is once daily. Fewer dosings are easier to remember. Properly taken medication is more likely to help than medication that is forgotten.

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Jonathan Stewart, M.D.

Dr. Stewart, who received his B.A. from Swarthmore College and his M.D. from Yale University, has worked at the DES since 1978. He is interested in the diagnosis and treatment of affective disorders, particularly in biologic and clinical measures that help treatment decisions.

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