Watch what you eat while taking medications…the example of Warfarin

Watch what you eat while taking medications…the example of Warfarin

By Manoja Eswara

When the doctor prescribes a medicine, the first thing a pharmacist explains is when and how to take the medication with respect to your meals. Food plays an important role in the way drugs are taken up and utilized by our body. While some drugs need to be taken before meals, some need to be taken with or after meals. Apart from this timing, increasing evidence shows that, the type and quantity of what you eat has a major effect on drug’s effectiveness. While some foods improve the drug action, certain foods can interact with and diminish the drug’s response. Unfortunately, the list also includes many foods that are considered very healthy under normal circumstances. Therefore it is very important to be aware of drug-food interactions and modify your food habits according to your prescription.

Warfarin (Coumadin) is a blood-thinning drug that helps in reducing clot formation and is often prescribed to patients with heart conditions such as blockage or heartbeat irregularities. Warfarin prevents clot formation by blocking Vitamin K, which is required for this process. Levels of Vitamin K in our diet directly affect how well Warfarin performs.  Excess intake of Vitamin K-containing foods would make it harder for Warfarin to be effective, leading to serious implications on health.

Vitamin K is an essential nutrient and we need on average 60-80 mcg per day.  Studies showed that slight deviations in Vitamin K levels could have big effects on Warfarin effectiveness. Therefore, it is very important to keep the levels of Vitamin K consumption consistent while taking Warfarin.

Here are a few examples of Vitamin K-rich foods to watch out for while taking Warfarin:

  • Green leafy vegetables including Kale, Broccoli, Cabbage, and Brussels sprouts etc are an excellent source of Vitamin K. While these greens are extremely healthy and are essential in your diet, you should consume consistent quantities thought out the treatment.
  • Avocados are another good source of Vitamin K, however the levels of Vitamin K vary greatly. Therefore, control your consumption of Guacamole.
  • Vegetable oils are rich in Vitamin K. Store bought products such as mayonnaise; margarine and salad dressings contain mix of different vegetable oils, and vary in their Vitamin K content. It is better to avoid them and opt for homemade alternatives instead.
  • Another variable source of Vitamin K that are known to interfere with Warfarin is dried herbs, herbal and dietary supplements. Make a list of supplements you use routinely and discuss them with your health care provider.
  • Grapefruit juice is notorious to interfere with many drugs, including Warfarin. Avoid eating grapefruit or drinking the juice. Same is true for cranberry juice.

Just like Warfarin-Vitamin K interaction, different foods interact with different drugs and it is very important to be aware of these interactions for your specific prescription.

Always read the drug labels.

Ask your doctor or pharmacist regarding foods to avoid, discuss your food habits and modify them before starting your prescription.

Let your health care provider know if and when you change your eating pattern.

If your blood coagulation levels are not well controlled your physician may consider alternative treatment options that have smaller impact on your diet.

Your genes also impact on warfarin response. Inherited variations in the VKORC1 gene which encodes the Vitamin K receptor,  and the CYP2C9 gene that controls warfarin clearance have substantial impact on warfarin dose.  Pillcheck can help you and your healthcare providers to choose best treatment options to fit your metabolism.


Important information to know when you are taking: Warfarin (Coumadin) and Vitamin K

Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for Pharmacogenetics-Guided Warfarin Dosing: 2017 Update

Warfarin FDA drug monograph

WARFARIN AND FOOD: A Guide for Patients

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