Chennai-based Orchid Chemicals & Pharmaceuticals Ltd. along with two other generic manufactures --- Sandoz and Abraxis Pharmaceutical Products sued Wyeth for unfairly delaying the entry of generic versions of blockbuster Zosyn in the US market. All three generic manufactures filed citizen petitions with the USFDA against Wyeth, after Wyeth received the U.S. Patent No. 6,900,184 (the ‘184 patent) on its blockbuster drug Zosyn, extending its patent life to 2023. U.S. Patent No. 4,562,073 (the ‘073 patent) covering tazobactam sodium, one of the key active ingredients of Zosyn will be running out patent protection on February 09, 2007. Wyeth discontinued its original formulation for Zosyn in November 2005 and subsequently launched a new patented formulation, delaying generic entry in the US market. According to the US FDA rules, a company is allowed to withdraw a product from the market only for reasons related to safety and efficacy. In case the product is withdrawn from the market, it is subsequently removed from the approved drugs’ reference list, and therefore no pharmaceutical company can market a generic version of this same drug. The generic manufactures challenged Wyeth approach, arguing that Wyeth is trying to extend the paten life of the drug and prevent the entry of generic players in the U.S. market. Generics further added while Wyeth has added an excipient to its drug, other players should be allowed to market generic versions of the original formulation for Zosyn. Orchid, Sandoz and Abraxis pharma already filed ANDAs in order to market a generic version of Zosyn’s original formulation in the U.S. The ‘184 patent particularly covers Wyeth’s re-launched Zosyn formulation comprising cryodesiccated powder of piperacillin sodium and tazobactam sodium along with edentate disodium dehydrate (EDTA) as a particulate formation inhibitor and sodium citrate as a buffer.