CVS posted second-quarter adjusted earnings, excluding certain items, of 65 cents a share, unchanged from a year earlier.

Net revenue fell 3.5% from a year earlier to $24 billion, the company said in a statement. Net income fell to $821 million from $886 million.

"The weak economy has had a dampening impact on prescription utilization and consumer behavior across the retail pharmacy sector," CFO David Denton said.

CVS cut its forecast for retail same store sales for the year to 2%-3.5%. It had previously forecast an increase of 3.5%-5.5%. The company also lowered guidance for adjusted earnings per share to a range of $2.68 to $2.73, from a range of $2.77 to $2.84. The reduction is partly due to the initial dilution related to implementation costs for the Aetna contract.

On Tuesday, Aetna awarded CVS a 12-year contract to provide pharmacy benefit management services. CVS will administer about $9.5 billion in annual drug spending to serve about 9.7 million Aetna members. CVS will also manage purchasing, inventory management and prescription fulfillment for Aetna's mail order and specialty pharmacy operations.