A hostile bidder for pharmacy benefits manager Caremark Rx is trying to buy time to win antitrust approval but Caremark derided the move as a "transparent ploy" to make shareholders believe that the deal has a chance.

ExpressScripts said it would withdraw its Hart-Scott-Rodino request for antitrust approval from the Federal Trade Commission this Friday, and refile it next week. The move would buy Express Scripts at least another 30 days to receive antitrust approval for a deal.