A case to point is the action that the FDA took when it withdrew its approval for a generic version made by Teva Pharmaceuticals of the popular antidepressant Wellbutrin. The reason for withdrawing the approval for this generic version was that as it turned out this version was not bioequivalent to the brand name.
The FDA was forced to do testing on this particular generic version after it received numerous complaints from patients that Teva's version had made them feel woozy, sick to their stomach or even suicidal. It turned out that the generic's active ingredient dissolved four times more quickly in the first two hours that of the brand name because of a different time-release mechanism. In addition on average Teva's product achieved a concentration in the blood ranging from 40% to 75% of the brand name Wellbutrin.
At a meeting of the FDA's advisory committee for clinical pharmacology in 2011 a prominent physician presented evidence of three different generic formulations of levothyroxine. All three were more potent from the branded version and varied from one another. One was 12.5% above, another 9% above and the third 3% above.
Another problem with generics is that an estimated 80% of active ingredients and 40% of finished medications come from overseas. In some cases they are manufactured in facilities that have not yet been inspected by the FDA. Quality can be compromised. For example recently the maker of a generic Lipitor, Ranbaxy Pharmaceuticals, recalled 480,000 bottles after tin shards of glass were found inside the pills.
In 2012 Congress passed the Generic Drug User Fee Ammendments bill. In it the generic drug industry agreed to pay the FDA $200 million dollars a year over five years to speed up the review and approval of generic drug applications and increase inspections of generic manufacturing plants abroad. This is certainly a step in the right direction.
Nevertheless almost all of us are or will be taking some generic medications. It is important to pay attention to how we respond to the medication and to be aware of any unusual physical symptoms that we may develop while on the medication. Our health may depend on it.