Washington (ChattahBox) - The three biggest U.S. pharmacy plan managers in the U.S., Medco Health Systems, CVS Caremark Corp, as well as Express Scripts Inc. have merged their electronic drug prescription networks under a single network, SureScripts-RxHub The new merged network, SureScripts-RxHub will be operated by a chain including Wal-Mart Stores Inc., Rite Aid Corp, Walgreens [...] ...