Express Scripts and other big managers of prescription medicine benefits for health plans said on Thursday they would no longer work with Philidor as concerns mount that Philidor was improperly directing drugs made by Valeant to patients. Valeant has since said it was cutting ties with Pennsylvania-based Philidor, and that the pharmacy was suspending operations.

"We are reviewing and evaluating all similar captive pharmacy arrangements that we know of and will work to identify others," said Brian Henry, a spokesman for Express Scripts. He defined a captive pharmacy as one that derives the vast majority of prescription volume from one manufacturer or one product.

(Reporting by Deena Beasley; Editing by Chizu Nomiyama)