The usual defense of this is to switch patients to new versions of the drug, including Bristol's Glucophage XR and Glucovance.

FORBES: Magazine Article

That also is creating doubts about whether Pristiq will be approved as an antidepressant, a major concern since Wyeth's top seller, the antidepressant Effexor XR, is expected to go generic next year.

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Quillivant XR received approval from the U.S. Food and Drug Administration on September 27, 2012, and is expected to be available in pharmacies in the U.S. in January 2013.

FORBES: The Molecule In Ritalin Keeps Generating Revenue