Public concern over the safety of generic drugs was further exacerbated by a Congressional investigation into bribery at the FDA by generics companies that found pervasive corruption; the investigation had been spurred by the generics company Mylan, which had hired private investigators based on its beliefs that competitors were getting unfair advantages in getting their generics approved.Mylan itself developed a version of a triamterene/hydrochlorothiazide combination drug after the Dyazide patent expired, and used a different, more stable formulation as well as different dosages of each active ingredient (50 mg hydrochlorothiazide and 75 mg triamterene, compared with Dyazides 25 mg hydrochlorothiazide and 50 mg triamterene) so it had to get approval as a new drug, as opposed to a generic; their product was called Maxzide and was approved in 1984. The higher dose allowed once per day dosing, which Mylan and its marketing partner, Lederle, believed would help it compete against Dyazide, which had $210M in sales in 1983.Mylans 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 Mylans Maxzide to obtain its bioequivalence data, leading both companies to withdraw its generic competitor to Mylans product. Generics eventually entered the market.
In 1986 Dyazide was the most prescribed drug in the US and had $325 million in sales, making it SmithKline Beckmans second-biggest seller behind Tagamet.The patents had expired on Dyazide in 1980, but complications arose with the introductions of generics, because the formulation of Dyazide resulted in variable batches that made it impossible for generic manufacturers to show that their versions were bioequivalent.Bolar Pharmaceutical was in the running to be the first to bring a generic, but its application was delayed by these concerns about whether its formulation provided the same amount of each drug; these were complicated by accusations that Bolar had fraudulently substituted Dyazide for its own version to conduct studies that were submitted to the FDA. Shortly after Bolars generic was approved, further concerns were raised with regard to Bolars applications to market generics more generally; these findings among others raised widespread concern among doctors and the public over whether generics were really the same as branded drugs. Bolar ended up recalling its generic form of Dyazide and withdrawing the product in 1990. In 1991 the US Justice Department on behalf of the FDA filed 20 criminal charges against Bolar for its fraud, and early the next year Bolar pled guilty and agreed to pay a $10M fine.