Warfarin – The Medication
Warfarin is the generic name for a medicine prescribed to people who are in danger of getting blood clots in their body and, therefore, having a stroke. It is often called a blood thinner but it is correctly called an anti-coagulant as it works to prevent clots forming in your body. It has been used for over 70 years.
If your warfarin dose is not steady you can be subject to headaches, dizziness, unusual bleeding and bruising, bleeding gums, nosebleeds, heavy menstrual periods and bleeding from cuts and injections which will not stop quickly. These side effects apply to all anti-coagulants.
Coumadin and Jantoven are the most common brand names for the medicine warfarin. The warfarin content of generic Warfarin, Coumadin and Jantoven may vary in content and strength and patients must be very careful if transitioning from one to the other.
Your medical team has judged that you are at risk of thrombosis or the formation of a blood clot inside your body which may stop the flow of your blood or move through your body and cause a stroke. Warfarin is prescribed to prevent further episodes if you have already had a blood clot, and to prevent the formation of future blood clots.
Your doctor will prescribe an appropriate dose but it may need to be adjusted over time. You must always take the dose prescribed and never alter it unless told to by your doctor. Try to take it about the same time each day. Do not panic if you miss a dose and do not double your dose next time. Your dose will be determined by your INR level.
INR stands for International Normalised Ratio. It represents the time it takes for your blood to coagulate. If someone not on a blood thinner clots their blood at a given time (represented by 1 in this case) and you have an INR of 2.3 it means that your blood takes 2.3 times the standard time of 1 to clot. This means that your blood has more time to move through a narrow or partially blocked area before clotting. Too low an INR and your risk your blood clotting where it should not. Too high an INR and you risk unwanted bleeds.
Your doctor will tell you the appropriate INR range for your condition. The number will differ according to your needs. If you have a valve replacement in your heart, the INR range may be different to someone in permanent atrial fibrillation.
Your doctor will provide you with a schedule. Usually, the tests are frequent to start with but, as you gain control of your dietary intake, and your body becomes used to the medicine, the tests may become less frequent. This change in frequency is quite normal.
Food and warfarin
Vitamin K1, found in many foods, is the problem. You are taking an anti-coagulant – Warfarin. Vitamin K1 is a coagulant. Therefore, one works against the other. The foods usually considered highest in Vitamin K1 are kale, spinach, broccoli, brussels sprouts, cabbage, collard greens (leafy fresh herbs), mustard greens, Swiss chard and most lettuces. However, in the Medical News Today, 12 February 2019, the American Heart Association added amaranth leaves, asparagus, endive, cress, green kiwi fruit, soybeans, tuna fish in oil, turnips and vegetable drinks to this list. Green tea and alcohol are also of concern.
There are two ways of managing your Vitamin K1 consumption:
‘dose to the diet’ – This means that you eat what you want, when you want, and the doctor will prescribe more medication to balance your INR. This is the most common approach in North America and some other countries.
‘diet to your dose’ – This means that you eat a consistent amount of Vitamin K1 daily so that your INR levels and your dose of Warfarin, can be stabilised. This is the recommended method of control from the manufacturers of Warfarin, Coumadin and Jantoven and from groups such as the Mayo Clinic and the University of Iowa Hospitals and Clinics in the USA, the Governments of Canada, Australia and many other countries.
Vitamin K1 is a fat-soluble vitamin. It role is to play an essential part in blood clotting. It gets its identifying letter from the German word Koagulation which is altered into English as coagulation. It is essential to your overall health. Never, ever take it as a supplement if you are on warfarin.
Vitamin K2 is also a fat-soluble vitamin. Its main role is to transport calcium to bones and cartilage but also prevents calcium depositions in the lining of blood vessel walls. It is mainly produced by the gut flora of bacteria in the body. It can also be found in butter, egg yolks, lard and animal-based food although, generally, in small quantities.
Across the world it is generally accepted that the Recommended Daily Allowance (RDA) of Vitamin K1 is 90mcg (µg) for women and 120 mcg (µg) for men. Patients on warfarin are often recommended to double that figure to allow more flexibility in their foods. To give you an idea of the limitations:
- ½ tablespoon of chopped chives = 85 mcg
- ½ cup of cooked cabbage = 82 mcg
- 1 cup of chopped water cress = 85 mcg
Recognised problems with warfarin
Yes. There are many options depending on the condition of the patient. If a rapid change is required either the administration of fresh frozen plasma (a form of blood transfusion) or a prothrombin agent can be used and will be effective with 10-15 minutes. An intravenous drip of Vitamin K will achieve coagulation within 4-6 hours. Oral Vitamin K will take about 24 hours to stabilise the blood. Withdrawal of the warfarin occurs in all the above instances. If no other intervention takes place after withdrawal, the presence of the drug will take days to disappear. (Ref: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1770479/)
The Mayo Clinic warns that many medications interact with warfarin. They list, specifically:
- Antifungal medications
- Aspirin products
- Acetaminophen (Tylenol, others)
- Cold or allergy medicines
- Medications, such as amiodarone, that treat abnormal heart rhythms
- Antacids and laxatives
- Coenzyme Q10
- Dong quai (often called female ginseng)
- Ginkgo biloba (also known as the maidenhair tree)
- Green tea
- St John’s wort
- Vitamin E
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