Bristol-Myers Squibb Co. said Monday it is recalling eight production lots of its anti-clotting drug Coumadin because the amount of the active ingredient in the drug could change.

The company said the recall is a precaution, and no side effects have been reported. Bristol-Myers Squibb is recalling a total of 144,672 1-milligram tablets of Coumadin, all of which were distributed in the U.S. The recall includes five production lots of Coumadin hospital unit doses and three lots of physician samples. All the tablets were distributed in blister packs. No bottled medicine or other doses are involved.

The New York-based company said the amount of isopropanol in the tablets could change over time. Isopropanol, or isopropyl alcohol, is used to keep the drug's active ingredient in a crystalline state. The changing levels of isopropanol could increase or reduce the amount of the active ingredient in the tablets.

Coumadin, also called warfarin, is a common blood thinner that is used to treat or prevent blood clots after surgery. Bristol-Myers Squibb said the risk of clots could increase if the level of active ingredient decreases, and if there is too much of the ingredient, patients face a greater risk of bleeding.

The tablets have expiration dates between June 2011 and November 2012.