Extended-release Formulations
Brand-name and generic bupropion tablets are available in three formulations, each as the hydrochloride salt: immediate release (Wellbutrin), sustained release (Wellbutrin SR), and extended release (Wellbutrin XL or XR). "Sustained release" and "extended release" are generally interchangeable terms, but in this case Wellbutrin SR is intended for twice-daily dosing and Wellbutrin XL is intended for once-daily dosing. Not all generics have retained this naming scheme, and the United States Pharmacopeia requires all prolonged-release drug formulations (including generics for Wellbutrin SR) to be labeled "extended release", which has caused confusion and medication errors. According to GlaxoSmithKline, the SR tablets should not be split. Merck indicates that splitting a 150 mg Wellbutrin SR tablet decreases the time to peak levels, but that it will retain its sustained-release characteristics.
Read more about this topic: Bupropion