WASHINGTON (AP) - The nation's two largest pharmacy benefit providers say they are severing ties with a mail-order pharmacy affiliated with embattled drugmaker Valeant Pharmaceuticals after a review of the pharmacy's business practices.

WASHINGTON (AP) The nation's two largest pharmacy benefit providers say they are severing ties with a mail-order pharmacy affiliated with embattled drugmaker Valeant Pharmaceuticals after a review of the pharmacy's business practices.

The news sent Valeant shares plummeting and raised new questions about the Canadian drugmaker's arrangements with Philidor RX Services.

A spokesman for CVS Health, the nation's second-largest pharmacy benefit provider, says the company terminated its business with Philidor because it didn't comply with terms of a provider agreement.

Separately, a spokesman for industry leader Express Scripts says the company is "in the process" of removing Philidor from its network. Express Scripts also said it is reviewing similar "captive pharmacy" situations, in which a pharmacy gets most of its business from one drugmaker.