NEW YORK (CNN/Money) - In an effort to avoid counterfeit drugs, CVS Corp. said it will no longer buy pharmaceuticals from wholesalers that trade in the secondary drug market.

CVS (down $0.15 to $55.00, Research), the country's biggest retail franchise, cited "rising concerns" that the secondary market "potentially provides an entry point for counterfeit and adulterated products to enter the legitimate pharmaceutical supply chain."

"CVS is taking what we believe to be the most effective means to ensure the continued integrity and authenticity of the pharmaceutical products that CVS dispenses to its customers," said Chris Bodine, executive vice president of merchandising and marketing at CVS, in a prepared statement.

Bodine said the Woonsocket, R.I.-based retailer will only purchase drugs "directly from the manufacturer, or from wholesalers who certify that they are not trading in the secondary drug market. If we are unable to receive those assurances, those wholesalers' contracts will not be renewed."

New York Attorney General Eliot Spitzer recently subpoenaed prescription drug wholesalers to investigate alleged price controlling in the secondary market.