In October the Food and Drug Administration took a highly unusual step: It declared that a generic drug it had previously approved -- a version of the popular antidepressant Wellbutrin -- was not in fact "bioequivalent" to the name-brand version. The FDA withdrew its approval.

The federal action shook the business. Teva Pharmaceuticals (TEVA), which marketed the generic in question, has stopped selling it, and other companies are now testing their versions of Wellbutrin at the FDA's request. The episode is bringing momentum to a movement that has been quietly building among many doctors and medical societies that are increasingly willing to ask a question that borders on heresy: Are generics really identical to the branded products they are meant to replicate? To a surprising degree, they say, the answer is no.

READ MORE: Click Here