Wow, to formulate a generic drug and export it to the U.S. requires the FDA stamp, but if you generate components used in manufacture of US-made drugs get literally no FDA oversight. How can this be?.
The FDA's legal basis to regulate medicines is actually incredibly weak and really hasn't changed much since the 1930s. One of the examples is exactly this case. The FDA only regulates finished medicines in two cases a) brand name or b) generic equivalents. Leaving aside brand name drugs for the moment getting approval to sell a generic equivalent doesn't look anything like what you would expect. What people generally think is that generic drugs are 'copies' of existing brand name drugs and the FDA cares about making sure the generic guys are producing the same drug as the brand name one.
This isn't what happens at all. A manufacturer has to demonstrate similar blood level uptake as the FDA approved equivalent drug using a very similar approval process for the brand name drug. This requires an incredible effort that is substantially the same as getting an original drug approved.
The bottom line is that the FDA doesn't examine the on-going manufacturing of the drug much or supplier reliability much at all. If a manufacturer can pass blood level equivalence nothing else really matters. This equivalence is only valid for the direct manufacturting producer of the drug, not the company marketing it. The reality is that if you want to get FDA approval for a generic you might as well partner with a firm outside the US that knows how to handle this process because its a waste of money jumping through FDA hoops to certify a new facility in the US.
Once you have proved equivalance you can start selling the drug. At this point, the FDA is basically done. The FDA basically dones't care anymore and has very weak sanctions to enforce safety compliance.
The FDA can't do anything about this situation on its own; the way drugs are approved is directly established by law that dates back to the 1930s. I notice a lot of people in this thread suggesting that FDA leadership is bought off and does the work of the drugs companies. I assure you this is not the case.
FDA oversight of pharmacutecial ingredients is accomplished under an entirely different legal regime that has nothing to do with drug approval whatsoever.