The company sold more prescription drugs, but lower payments from insurers ate into its profits. Low reimbursement rates, coupled with disappointing performance at its British Boots unit and sluggish retail growth, have hammered its stock. It was the Dow's worst performer last year, sinking nearly 14%.

That stock tumbled Wednesday- making it the day's biggest decliner on the Dow and S&P 500.

The company explored going private last year. But Reuters sources say many private equity firms are reluctant, concerned about its business prospects and the challenges of financing a buyout.