Vital Finds: The Herb - Drug Mix

Deciding what's safe...

By Robert Rountree, M. D. co-author of Smart Medicine for a Healthier Child

Millions of people regularly take blood-thinning drugs such as warfarin, and even more take aspirin and similar medications to prevent heart attacks and strokes. At the same time, with the use of herbal medicines more popular now than ever, surveys, show that most people don't tell their physician about their use of herbs or vitamin supplements.

How do herbs & Blood thinners mix?

Herbs may interact with the blood thinning drugs in different ways, some of them beneficial, some of them potentially harmful.

Herbs that enhance the effect of anticoagulants may have antiplatelet activity, meaning that they keep platelets from forming clots, or anticoagulant activity, meaning that they increase the time it takes a clot to form, usually because they contain a compound called coumarin.

Other herbs may counteract the effect of anticoagulants by decreasing blood-clotting time, most likely because they contain a coagulant called berberine.


Herbs with Anticoagulant Activity
Chamomile, Dong Quai, Horse chestnut

Herb as Coagulants (blood thickeners)
Goldenseal, Oregon grape root, Shepherd's purse

Herbs with Antiplatelet Activity
Bilberry, Bromelain, Cayenne, Feverfew, Flaxseed oil, Garlic, Ginger, Ginkgo Biloba, Ginseng, Green Tea, Meadowsweet, Motherwort and Turmeric



Meanwhile, physicians are starting to realize that many herbs posses potent pharmacological activity. Concerns have been raised in prominent medical journals that this activity could have detrimental effects, especially for patients taking certain types of medication. Cautious physicians have chosen the route of absolute avoidance - rather than risk an adverse reaction, they recommend that patients stop taking herbs altogether.

Is this rational policy? Or is there another approach somewhere in between? To better answer these questions, let's look more closely at how anticoagulants, or blood thinners, work in the body.

Blood Thickening and Thinning

Warfarin is the most commonly prescribed anticoagulant drug. Doctors typically give anticoagulant to people with high risk of blood clotting, such as those who have artificial heart valves, deep vein thrombosis (a large blood clot) in the legs, or arterial fibrillation (a chronic irregularity in heart rhythm).

The process by which blood thickens into a clot involves a chain reaction: Various proteins interact to produce thrombin, which then produces fibrin, the protein material the forms the clot's core. Several of these interacting proteins are made in the liver, where vitamin K ( from the Danish koagulation) is essential for their production.

Warfarin inactivates vitamin K to limit clotting proteins, so it increases the amount of time it takes for blood to clot. This effect can be monitored with a simple blood test called the prothrombin time (PT).

Vitamin K is found in high concentrations in many foods, including dark green leafy vegetables (especially turnip greens), alfalfa sprouts, broccoli, asparagus, egg yolks, and dairy products. Eating these foods increases the potential for higher blood levels of vitamin K, which would interfere with the anticoagulants. A few herbs also promote clotting, most notably shepherd's purse, possibly because it contains vitamin K.

Another aspect of blood clotting involves the clumping together of platelets. The combination of platelet clumps and the fibrin clot is what causes blood to thicken into full-blown clots. Platelet function can be measured in most doctor's offices with a test called the bleeding time. Many antiplatelets agents (which keep platelets from sticking together) are commonly used in medical practice, primarily to prevent strokes and heart attacks.

Aspirin is the most common antiplatelet agent; others include dipyridamole (Persantine), sulfinpyrazone (Anturane), clopidogrel (Plavix), and ticlodipine (Ticlic). Many herbs also inhibit platelet aggregation. Undoubtedly this list will expand with further research.



If using anticoagulants has slowed a person's normal clotting mechanism, good platelet function is obviously an important backup system. Otherwise, a minor injury could lead to a severe hemorrhage. Or, if you're taking antiplatelet drugs everyday, the addition of ginkgo or one of the herbs listed in the first two sections of the chart above could lead to uncontrolled bleeding.

Deciding what's Safe

So what is an informed person to do? Well, there are several options, depending on the degree of effort one is willing to put out. As a start, I propose the following step-by-step method.

• If your doctor starts you on anticoagulant medication and your diet already includes vegetables rich in vitamin K (or a multivitamin that includes vitamin K), it's not necessary to make any dietary changes. Instead allow your doctor to adjust the dose of medication based on the PT test. In this situation, it's more important that your diet remain constant without any sudden changes. If you do need to make changes, inform your doctor so that the PT can be checked right away.

• While you're taking anticoagulants, avoid regular use of concentrated, standardized extracts of herbs that are known to have antiplatelet activity, such as ginkgo, which is commonly sold as 50:1 concentrate. While a daily cup of ginkgo tea or dropperful of tincture is unlikely to cause problems, the extract is much more potent. The same rationale applies to concentrated forms of any of the antiplatelet herbs, although it's probably safe to eat fresh ginger or garlic in food or to have a cup or two of green tea every day.

• If you feel that it's essential to your health to continue taking any of the anticoagulant / antiplatelet herbs listed in the chart below along with the prescription, there's another option. Ask your doctor if he or she would be willing to monitor your bleeding time stays in the normal range, you're less likely to have an unexpected hemorrhage.

• If you're generally healthy and taking an antiplalelet drug such as aspirin for preventive purposes, you may want to try switching to ginkgo, which has many benefits. And consider that deep-sea fish oils (salmon, cold) have many of the same positive effect as aspirin, without the risks.

Thoughtful Research

Given the increasingly large number of people taking complex mixtures of herbs, vitamins, and drugs, it's probable that we will see more reports of side effects and negative interactions. Some authorities are using these incidents to discourage the public from taking herbs. But rather than turning back the clock on herbal medicine, I propose learning from these examples and upgrading our database of medical information.

Source: Herbs for Health magazine