A tiny fraction of drugs get repurposed in this manner and an even tinier fraction are blockbusters--so this windfall notion is a red-herring. Regardless, all of those drugs have to go through FDA trials to be labeled for the repurpose--a process which is not overnight or inexpensive.

You're correct that sometimes drug companies create new flavors or drug combinations and patent those--as with nexxium--but the original patent is still expired and a generic still available. If patients chose the new drug because it's one pill instead of two, the problem is not with the drug companies.