From the FDA:
May 2, 2011 - Bristol-Myers Squibb initiated a voluntary recall of one lot of 1,000-count bottles of Coumadin® (warfarin sodium) Crystalline 5 mg tablets. Bottles of 1,000 tablets are distributed to pharmacies for further dispensing to patients in prescription quantities. The lot number affected in the U.S. is 9H49374A with an expiry date of September 30, 2012. The recall is a precautionary measure based on the company’s testing of tablets from a returned bottle. A single tablet was found to be higher in potency than expected.