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The Herb Drug Mix

The herbs and drugs that you shouldn't mix
By Robert Rountree, M.D.
July/August 1999
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There’s been a lot of confusing news lately about mixing botanicals and pharmaceuticals. What’s safe, what’s not? Here, Herbs for Health kicks off a regular column by medical doctor Robert Rountree, who will clear up the confusion and offer guidelines for safely ­combining medicine of both the botanical and pharmaceutical kind. This issue’s topic: the impact of herbs on blood-thinning drugs such as aspirin and warfarin.

Cautious doctors have chosen to avoid herbs, but is this rational?

Maggie, a patient in my ­family practice, has a dilemma. One of the valves in her heart was ravaged by rheumatic fever when she was a child. Now, at age sixty-eight, Maggie has just had the valve replaced with an artificial one.

Before the surgery, she had done her best to achieve a healthy lifestyle and ate a diet rich in fresh fruits, vegetables, and many herbs, including ginkgo and garlic. But after surgery, her doctor started her on a drug called warfarin (its brand name is Coumadin), intending to thin her blood so that it would take longer to clot. Along with the drug, he gave her two recommendations: Stop eating green, leafy vegetables, and stop taking ginkgo and garlic supplements.

On the one hand, Maggie trusts her surgeon. On the other, she has noticed that her memory has improved from taking ginkgo, and she counts on the green, leafy vegetables to provide her with rich sources of vitamins such as folic acid and carotenes. But she has to wonder—is it safe to discount her surgeon’s advice?

Maggie is not alone. 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 physicians about their use of herbs or vitamin supplements.

Meanwhile, physicians are starting to realize that many herbs possess 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 medications. In particular, there are reports of patients developing bleeding in the brain and eye after taking standardized ginkgo extracts. Cautious physicians have chosen the route of absolute avoidance—rather than risk an adverse reaction, they recommend that patients stop taking the herb altogether.

Is this a 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 anticoagulants to people with a 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 that 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 (see page 54 for more ­information).

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 doctors’ ­offices with a test called the bleeding time. Many antiplatelet 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 (Ticlid). Many herbs also inhibit platelet aggregation (see page 54). 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 every day, the addition of ginkgo or one of the herbs listed in the first two sections of the chart on page 54 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.

q 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.

q While you’re taking anticoagulants, avoid regular use of concentrated, standardized extracts of herbs that are known to have antiplatelet activity (see page 54), such as ginkgo, which is commonly sold as a 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. This 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.

q If you feel that it’s essential to your health to continue taking any of the anticoagulant/antiplatelet herbs listed on page 54 along with the prescription, there’s another option. Ask your doctor if he or she would be willing to monitor your bleeding time along with the PT. If your bleeding time stays in the normal range, you’re less likely to have an unexpected hemorrhage.

q If you’re generally healthy and taking an antiplatelet 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, cod) have many of the same positive effects as aspirin, without the risks.

q If you’re taking an antiplatelet medication because you are at high risk for stroke or heart attack, it may not be advisable to take standardized extracts of antiplatelet or anticoagulant herbs. The higher the dose and potency of the medication, the greater the risk. For example, if you’re taking one “baby” aspirin a day, your chance of bleeding is less than if you’re taking four adult-strength tablets a day. If you feel a strong need to take the herb and the drug, have your bleeding time measured regularly to be certain it doesn’t exceed a healthy range.

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. As more potent herbal concentrates become commercially available, it’s essential that we study their pharmacology in detail, so that informed consumers—and, hopefully, informed health-care practitioners—can have ready ­access to up-to-date accurate information regarding potential risks and benefits.

Robert Rountree, M.D., is a physician at the Helios Health Center in Boulder, Colorado, where he practices integrative medicine. He is coauthor of Smart Medicine for a Healthier Child (Avery, 1994) and an Herb Research Foundation advisory board member.


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