Coumadin Clinic

 

Warfarin (Coumadin®) Drug Interactions -

 

Numerous medicines can interact with warfarin. This includes prescription and over-the-counter medicines, and herbals. Taking warfarin with these medicines can increase your chances of clotting or bleeding. Many interactions can be very serious, even fatal. For this reason, it is important that you check with your doctor or pharmacist before starting any new medicine while on warfarin. It is also important that you report any changes in your medicines to the clinician monitoring your warfarin.

Over-the-counter medicines that can increase the effects of warfarin are listed in Table 1. Tylenol® has been reported to increase the effects of warfarin when large doses are taken for a duration of greater than one week. Many cough and cold products contain some of the pain medicines listed, so it is important to check with a healthcare provider before taking these medicines.

 

Table 1

 


Several herbals and supplements can also interact with warfarin. Herbals are of particular concern to healthcare professionals. Many people do not consider herbals to be “drugs.” It is important to note that herbals are not regulated by the Food and Drug Administration.

Their potency can vary from product to product, which can affect the severity of the interaction. Herbals that can increase or decrease the effect of warfarin are listed in Table 2. Supplements that contain vitamin K can decrease warfarin’s effect and can lead to clotting.

 

Table 2

 


There are also many prescription medicines that can interact with warfarin. Some of the more common prescription drug interactions with warfarin are listed in Table 3.

 

Table 3

 

This information does not include every medicine that interacts with warfarin. It is very important to check with a doctor or pharmacist before changing any medicine, including over-the-counter, prescription, and herbals.