Complementary Alternative Cardiovascular Medicine

Chapter 4 / Herb and Dietary Supplement Interaction 51
Several herbs have exhibited varied potential for improving cardiovascular
conditions (11), particularly hawthorn, garlic, ginkgo, and horse
chestnut. Hawthorn (Crataegus spp.) leaves, flowers, and berries are the
most widely used cardiotonic preparations in Europe; the plant is used
primarily for angina, cardiac dysrhythmias and mild hypertension (5).
Garlic (Allium sativum), which is claimed to impart several health benefits
(15–18) is most promising for its antithrombotic effect (19). Ginkgo
(Ginkgo biloba) has been used for treating arterial occlusive disease (20)
and judged particularly effective for intermittent claudication (21). Horse
chestnut (Aesculus hippocastanum) is effective in treating chronic venous
insufficiency (CVI) (22). In addition, the nonherbal endogenous antioxidant,
coenzyme Q10 (CoQ10 or ubiquinone), is beneficial in treating heart
failure, angina, and essential hypertension (23); in 1974 the Japanese government
approved its use to treat congestive heart failure (CHF).
Numerous medicinal herbs, including garlic and ginkgo, as well as
CoQ10, have been implicated as having potential for adverse drug-interaction
effects. These last three substances have been cited for their possible
interference with the blood-clotting process, which is relevant for
patients who are at risk for bleeding or taking anticoagulants. This is an
important consideration, particularly when drugs with narrow therapeutic
windows are involved, such as the anticoagulant warfarin (Coumadin)
and the cardiac glycoside, digoxin.
ANTICOAGULANT–ANTIPLATELET INTERACTIONS
The potential for interaction of coumarin anticoagulants with a host
of medicinal herbs has been advanced. Many of the proposed cautions
relate to herbs for which some type of in vitro activity has been observed,
which may have an influence on the blood-clotting process: one or more
of the vascular, platelet, and coagulation phases. The anticoagulant
potentials of feverfew (Tanacetum parthenium), ginger (Zingiber
officinale), and especially Asian ginseng (Panax ginseng), which is often
advanced in the company of ginkgo, are highly questionable and likely
inconsequential in the clinical context. Although feverfew extracts and
its sesquiterpene lactone constituents, notably parthenolide, inhibit platelet
aggregation by inhibiting serotonin release, among other actions (24),
no reports can be found in the literature of bleeding episodes or alterations
in bleeding time that are associated with feverfew consumption.
A similar situation obtains for ginger, which also inhibits platelet aggregation
in vitro, because it is a potent inhibitor of arachidonic acid, epinephrine,
adenosine diphosphate, and collagen (25). Although there is
no evidence for an interaction of either feverfew or ginger with coumarin