A number of medications may interact with warfarin. Interactions could lead to life-threatening problems, such as strokes, blood clots, and internal bleeding. In order to reduce your risk of developing potentially serious drug interactions, it is important to talk to your healthcare provider every time you start, stop, or change your dosage of any medication, including non-prescription medications.
Warfarin sodium (Coumadin®, Jantoven®) is likely to interact with many different medications, far too many to list here. In fact, more than 50 different categories of medications interact with warfarin (usually with many individual drugs within each category). It is good practice to assume that any medication or supplement (such as dietary or herbal supplements) can interact with warfarin, unless your healthcare provider specifically tells you otherwise.
It should also be noted that warfarin may also interact with foods (see Coumadin Diet for more information).
It is probably not a good idea to rely on the Internet or books for up-to-date information on warfarin drug interactions. Information about drug interactions is constantly changing, and information from the Internet or books could be outdated. Even the prescribing information ("package inserts") for medications should not be relied upon, as it may take awhile for this information to be updated and put into print.
Your healthcare provider should have access to resources on the most current information about interactions with warfarin. Specialized "warfarin clinics" are particularly good at keeping up to date with current information regarding drug interactions.