Shortage of warfarin sodium tablets

The American Society of Health-System Pharmacists reports a shortage of warfarin sodium tablets. Actually only Coumadin, the brand name product from Bristol-Myers Squibb, is in short supply, and the manufacturer did not give a reason. The importance of this ASHP bulletin is contained in this quote: "Interchanging products between manufacturers is not recommended and could lead to altered INR levels." If you are taking Coumadin and must switch to a generic version of warfarin, the doses may not be equivalent. This is an exception to the rule that generic drugs must be equivalent to brand name drugs. It is based on the fact that the therapeutic dosage range of warfarin is narrow compared to most drugs, and too little or too much effect  is a real possibility when switching tablet makers.