Teva Pharmaceutical has been forced to pull its generic version of the extended release formulation of GlaxoSmithKline's antidepressant Wellbutrin after authorities determined it was not therapeutically equivalent to the branded medicine.
The announcement comes six years after the Food and Drug Administration (FDA) first became aware of a possible problem with Budeprion XL 300mg, which is manufactured by Impax Laboratories and marketed by Teva in the US, following reports that patients who were switched from Wellbutrin XL 300 mg to its generic counterparts were experiencing reduced efficacy.
FDA analysed these reports at the time and concluded that the complaints appeared to be linked to the Impax-Teva product.
The agency then asked Impax and Teva to conduct a study directly on its 300mg extended-release product to compare its bioequivalence to Wellbutrin XL 300 mg, but this study was terminated in late 2011 after Impax and Teva were unable to recruit a significant number of affected patients to generate the necessary data.
The FDA had already decided to sponsor its own study in 2010, however, involving 24 healthy adult volunteers. This study was designed to measure both the rate and the extent of release of the active pharmaceutical ingredient bupropion into the blood.
The results of this study became available in August 2012, and showed that the generic product tablets failed to release bupropion into the blood at the same rate and to the same extent as Wellbutrin XL 300mg.
The FDA has not conducted bioequivalence studies of the other four generic versions of Wellbutrin XL 300mg, which are marketed by Anchen, Actavis, Watson, and Mylan.
However, all four companies have been asked to conduct their own studies, with data to be submitted no later than March 2013.
The FDA said it will review the data from these additional studies when they are received,although the agency believes the results are likely to be unique for the Impax-Teva version.
In addition, the FDA clarified the announcement does not affect the 150mg version of Impax-Teva's Budeprion.
As reported by Bloomberg, Teva spokesperson Denise Bradley said: “There is no material impact to Teva. We have no comment on whether we will launch our own version of this product at this time.”