For patients who want a less expensive generic, he recommends sustained release (SR) because there does not seem to be a clinical difference between the brand name and generic versions in that form. SR has to be taken twice a day, while XL is taken once a day.
"If it were me and I could afford it and/or my insurance company allowed me to take it, I would err on the side of caution and take the brand name until the generics were proven at the higher doses to be bioequivalent," said Dr. Sheldon Preskorn, a professor of psychiatry at University of Kansas School of Medicine-Wichita.
The FDA decided to study the bioequivalence of bupropion XL 300 mg made by Impax/Teva to the brand-name counterpart because of adverse events that had been reported to the agency since the generic was approved in 2006.
"The adverse event reports we got included loss of antidepressant effect and, in some instances, worsening of depression symptoms, following a switch from the brand name to a generic product," Walsh said.
Some patients also reported that adverse effects associated with bupropion, including headache, fatigue and anxiety, got worse after switching to Impax/Teva's generic version, Walsh added.
About half of these patients said their depressive symptoms and adverse events improved after switching back to Wellbutrin XL 300 mg, according to the FDA.
"Relapsing of major depression is not inconsequential," Preskorn said. "Major depression causes problems with social functioning, work performance and some level of a suicide risk."
For the bioequivalence study, the FDA measured the level of Wellbutrin and bupropion XL 300 mg in the blood of 24 healthy adult volunteers over the course of the day after taking the medications.
The FDA requires the level of generic drug absorbed in the blood to be, on average, within 80 and 125 percent of the level of the brand-name version. However the range of absorptio
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