Warfarin sodium (Coumadin®, Jantoven®) is a prescription anticoagulant, often described as a "blood thinner" (although it does not actually thin the blood). It is used to prevent and treat blood clots due to various causes. As with most medications, it is possible to take too much warfarin. However, unlike many other medications, even just a little too much warfarin can be extremely dangerous.
The most important effect of a warfarin overdose is bleeding. This can include obvious bleeding (such as vomiting of blood, nosebleeds, or bright red blood in the stool) or bleeding that is less obvious (such as internal bleeding). An overdose can occur in several different ways. Besides an intentional overdose, an overdose with warfarin can occur as a result of certain food or drug interactions.
The antidote for a warfarin overdose is vitamin K, which can be given in tablet or injectable form. These treatments must be done carefully. If too much vitamin K is given, this can reverse the effect of warfarin so much that it is no longer effective for preventing blood clots. If too little is given, the risk of bleeding will persist.
(Click Coumadin Overdose to learn more about the signs and symptoms of a warfarin overdose and to find out what treatment options are available for severe overdose cases.)