WASHINGTON, July 23 (Reuters) - U.S. rules, aimed at ensuring prescription medicines are not misused, have been manipulated by brand-name drug companies to keep cheaper competition off the market, costing consumers billions of dollars, a report said on Wednesday.

Protections set up by the U.S. Food and Drug Administration called "risk evaluation and mitigation strategies" (REMS), which can curb distribution of dangerous medicines, have been used to prevent generic drugmakers from getting the drugs in order to test their own versions, which is required to win FDA approval, the report from the Generic Pharmaceutical Association said.

This has delayed the arrival to market of 40 potential generic drugs, costing consumers some $5.4 billion a year, according to the report by Matrix Global Advisors and released by the generic drug trade group.

GPHA's members include Impax Laboratories, Inc ; Perrigo Pharmaceuticals; Ranbaxy, Inc; Sandoz US; Teva Americas and Apotex Corp, among others.

(Reporting by Diane Bartz; Editing by Ros Krasny and Bernadette Baum)