Interactions between essential oils and coumadin (warfarin)

Recently one of my students posted to our student/graduate group asking whether any essential oils would be contra-indicated for someone on Coumadin and I thought that this would be a good topic for the blog.

Coumadin, one of the brand names for warfarin, is an anticoagulant. Originally it was launched in 1948 as a rat poison and is in fact still available for this purpose. At first it was thought to be too toxic for human consumption, however in 1951, the failed suicide attempt of a navy recruit who had taken a large dose of rat poison led clinicians to discard dicumarol in favour of warfarin. The first clinical study with warfarin was reported in 1955. In the same year, President Eisenhower was treated with warfarin following a heart attack. In the early 1950’s it was approved for use as a medication and today it is the most widely prescribed anticoagulant drug in North America. However, there is a downside, warfarin can interact adversely with a number of commonly used medications as well as some foods. It is important therefor that its use is monitored by frequent blood testing to ensure that an adequate and safe dose is being taken. There is a lot of information available on the web on coumadin (warferin) however here is a summary of some of the cautions to keep in mind.

  • Warfarin is contraindicated in pregnancy.
  • The only common side effect of warfarin is hemorrhage (bleeding).
  • The risk may also be increased in elderly people.
  • Avoid sudden changes in dietary habits. Avoid ingesting unusual increases or decreases of foods high in Vitamin K (liver, broccoli, cauliflower, cabbage, kale, spinach and other green leafy vegetables, green tea, certain vegetables, cheeses and certain vitamin supplements). It is best to avoid strictly vegetarian diets that consist of foods high in vitamin K.
  • Many commonly-used antibiotics, will greatly increase the effect of warfarin by reducing the metabolism of warfarin in the body. Other broad-spectrum antibiotics can reduce the amount of the normal bacterial flora in the bowel, which make significant quantities of vitamin K, thus potentiating the effect of warfarin.
  • Thyroid activity also appears to influence warfarin dosing requirements.
  • Excessive use of alcohol affecst the metabolism of warfarin and people taking warfarin are often cautioned against the excessive use of alcohol.
  • Many drugs interact with warfarin.

Warfarin also interacts with many herbs and spices, both those eaten in food (e.g. ginger and garlic) and those used for medicinal purposes (e.g. ginseng and Ginkgo biloba). All may increase bleeding and brusing in people taking warfarin; similar effects have been reported with borage (starflower) oil or fish oils.St. John’s Wort, sometimes recommended to help with mild to moderate depression, interacts with warfarin; it induces the enzymes that break down warfarin in the body, causing a reduced anticoagulant effect.

And what about essential oils?

Methyl salicylate is the component to be aware of. When applied topically to the skin it is absorbed transdermally without any problem, quickly finding its way into thebloodstream and once there it can potentiate the anticoagulant effect of warfarin and could cause internal hemorrhage. Methyl salicylate is a component found in many liniments, however it is also found in large quantities in the essential oils ofSweet Birch (Betula lenta) and Wintergreen (Gaultheria procumbens) both of which are composed of naturally occurring methyl salicylate at around 98 – 99%. This makes it a very easy oil to adulterate by simply adding synthetic methyl salicylate. While there are those who find these oils to be very effective in sports therapy, muscle blends etc, if you must use then, do it with great care and only over very short periods of time.

Robert Tisserand and Tony Balacs, in their book Essential Oil Safety, say: These oils should not be used in therapy, either internally or externally. Do not use if taking anticoagulants (e.g. aspirin and heparn).

Also in Essential Oil Safety, Robert Tisserand and Tony Balacs have a listing on bloodclotting mentioning that both garlic and onion oils demonstrate anti-platelet activity which is essential for blood clotting. However these are not two oils that one would find in most aromatherapist’s kit. They do however say that :

Anti-platelet activity is also demonstrated by eugenol and iso-eugenol and is due to an anti-prostaglandin action. It would be prudent to avoid oral administration of garlic oil, onion oil, and all eugenol-rich oils in those with blood clotting problems. This group includes people with haemophilia, liver disease, kidney disease, prostate cancer and systemic lupus erythematosus. It would be prudent for anyone taking anticoagulant drugs, such as aspirin, heparin and warfarin to avoid oral use of the same group of oils.

Note the method of use they are talking about is oral. All the other references for contra-indications for herbs and warfarin I was able to find in the reference books I have on drug-herb-vitamin interactions were also for the oral use of the herb. If you wanted to carry this over to the use of the essential oil, then it would pertain to the oral use of the essential oil. With the exception of Birch and Wintergreen, essential oils applied topically on the skin or by one of the inhalation methods should not present a problem. Oils taken internally might. Another reason why we don’t recommend the internal use of essential oils unless one has had specific, extensive training in that method.

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