What should I know about drug interactions?
Warfarin interacts with many prescription and over-the-counter (OTC) medicines. OTC medicines can be found in the aisles at a pharmacy. This includes vitamins, herbals, and natural products. Bring a list of all the medicines you take to your visits so they can be checked for drug interactions.
It is very important for you to check with your care team before starting, changing, or stopping any medicine. You may need more frequent INRs or changes in your warfarin dose if you have changes in medicines.
The following is a list of some OTC medicines you should not take, unless told by your care team. These lists do not have everything that may interact with warfarin. It is very important to check with your pharmacist if there are any changes to your medicine while on warfarin.
Common OTC medicines that affect warfarin:
- Aspirin or ointment and cream with aspirin, such as Aspercreme®
- Pepto-Bismol® and some Alka-Seltzer®
- Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Motrin® or Advil®) or naproxen (Aleve®)
- Vitamin supplements with vitamin K
Some common prescription medicines that affect warfarin:
- Antibiotics, such as:
o Sulfamethoxazole/trimethoprim (Bactrim®)
o Ciprofloxacin, moxifloxacin (Avelox®)
o Metronidazole (Flagyl®)
o Rifampin, dicloxacillin, nafcillin - Yeast or fungal medicines, such as fluconazole
- Thyroid medicines, such as levothyroxine
- Amiodarone (a heart medicine)
- Carbamazepine (a seizure medicine)
- Paxlovid® (used for COVID-19)
Some common herbals that can affect warfarin are:
- Coenzyme Q10
- Garlic
- Ginkgo biloba
- St. John’s wort