Walgreen Co., the drugstore chain, sued Endo International and Impax Laboratories over allegations that the two companies conspired to keep generics of the pain medication Opana ER off the market.

Along with Walgreen, grocery chains Kroger, Safeway, Albertson’s and HEB have accused Endo of paying Impax “more than $112 million in cash in exchange for Impax’s agreement to delay the launch of its less-expensive versions of Opana ER for two and a half years,” reported Bloomberg News.

This alleged transaction is what is considered a pay-for-delay deal, which is an agreement by two companies to postpone a drug’s introduction to the marketplace.

The Supreme Court ruled in 2013 that the Federal Trade Commission could sue pharmaceutical companies over pay-for-delay deals but did not say that the arrangements were illegal, The New York Times reported at the time. The Wall Street Journal reported in January that the FTC said it is too early to see if the decision has “had an impact on the extent to which these agreements may be viewed as anti-competitive.”

The complaint alleges that Endo spent the time trying to convert patients to an abuse-resistant form of the painkiller, forcing the companies to pay more money for these medications than they would have if a generic had been available. Bloomberg noted that 11 other cases against Endo are also pending.

Lawsuits are not the only reason Endo’s Opana is in the news. The painkiller has been tied to Indiana’s worst HIV outbreak. The New York Times said the jump in HIV infections in Indiana “stems largely from the intravenous use of prescription painkiller Opana.”