Mylan's patents on the drug were declared invalid in court, and its marketing exclusivity expired in 1987, prompting a rush of generic competition and litigation by two of them, American Therapeutics Inc. and Vitarine Pharmaceuticals, with the FDA. Vitarine, along with Par Pharmaceutical, were two of the companies that Mylan had targeted in its investigation into corruption and it turned out that Par and Vitarine had each used Mylan's Maxzide to obtain its bioequivalence data, leading both companies to withdraw its generic competitor to Mylan's product. Generics eventually entered the market.