When I joined the staff of a hospital six years ago, I began to have a greater awareness of the pharmacologic activity of herbs and dietary supplements and how they interact with drugs. I had practiced naturopathic medicine for 15 years prior to this, but because naturopathy is not based on use of pharmaceuticals, I was far less focused on potential interactions than my allopathic colleagues were.
A survey of 2,000 adults conducted in 1999 by Prevention magazine and Princeton Survey Research Associates revealed that 31% of consumers used herbs with prescription drugs and 48% used herbs with OTC medications. Consequently, concern about possible drug-herb/supplement interactions was thrust into professional and public consciousness as a topic of considerable importance.
Most of the media attention has focused on the potential for harm when supplements are combined with drugs. However, data on potentially harmful interactions are often preliminary, and the concerns are sometimes more speculative than scientific. None the less, governmental authorities feel compelled to err on the side of extreme caution, to the point of neglecting traditional wisdom and clinical experience in some cases.
One point that has been consistently overlooked is that many interactions between nutrients or herbs and drugs may actually be beneficial. For example, a natural product may potentiate the action of a drug, allowing for a dose reduction and a concomitant decreased risk of side effects. Certain herbs or nutrients may increase the therapeutic effect of a drug, as has been seen in numerous studies with antioxidants and cancer chemotherapy.
The nurse in the outpatient oncology program at North Hawaii Community Hospital and my colleagues at the Cancer Treatment Centers of America can testify that the patients who are utilizing adjunctive natural medicines under the direction and supervision of naturopathic physicians, generally tolerate chemotherapy much better than those who do not receive such care.
Most herbs and supplements are quite safe when used in appropriate dosages, but they are sometimes able to exacerbate the toxicity of prescription drugs. For example, the neurotransmitter effects of St. John’s Wort’s interact with MAO inhibitors and SSRI’s, increasing the already significant risk of adverse effects from these medications.
Since the bulk of attention has been focused on safety issues and potentially dangerous interactions, many of which are theoretical, I would like to emphasize some concrete examples of beneficial interactions that occur with drugs and natural medicines, as seen in clinical practice.
Statins and CoEnzyme Q10
A serious concern still exists about the potential adverse effects of cholesterol lowering statin drugs, since they inhibit not only the production of cholesterol but also the synthesis of coenzyme Q10 (see related story, pp. 1–2). We are in the midst of a dramatic increase in CHF in the US. Are we, as doctors, contributing to this epidemic through over-zealous use of statins? The risk of statin-associated cardiomyopathy could be easily reduced by supplementing with Co-Q10. This is a clear example in which combining a nutrient with a drug is not only safe, but also makes strong biochemical and clinical sense.
Metformin and Vitamin B12
Metformin, the insulin-sensitizing drug used for diabetes and polycystic ovarian syndrome, is another commonly prescribed drug which causes a treatable nutritional deficiency (see HPC April 2002). Metformin interferes not only with glucose absorption in the gut, but with the calcium-dependent cell membranes that absorb vitamin B12. Long-term B12 deficiency manifests as peripheral neuropathy. B12, along with vitamin B6 and folic acid, is also responsible for metabolizing homocysteine into less harmful substances. Over eighty studies have shown that elevated homocysteine greatly increases the risk of atherosclerosis. A recent study revealed that taking a calcium supplement prevented the B12-induced deficiency caused by Metformin, thereby improving B12 absorption. Those taking Metformin should be taking supplemental calcium, vitamin B12, B6, and folic acid.
Dietary Supplements and Platelet Aggregation
The effects of phytomedicines and nutritional supplements on platelet function are one of the most pressing areas for research in natural medicine. Since several anecdotal reports were published about hemorrhages in patients taking Ginkgo biloba, many warnings have been made about combining natural products with anti-thrombotic medications such as aspirin and coumadin. However, a recent randomized study of 90 men and women 65–85 years old found that four months of supplementation with a product containing Ginkgo biloba 160 mg/d, DHA 200 mg/d, and Gotu kola 68 mg/d, had no effect on primary hemostasis (Carlson JJ, et al. Experimental Biology 2002).
Much more research is needed to quantify the effects on platelet aggregation of other substances including bromelain, curcumin, Vitamin E, garlic, ginger, and eicosapentahexaenoic acid (EPA). And I believe it is far too soon to condemn a number of potentially helpful herbs and nutrients simply based on the theoretical risk that they may potentiate the anticoagulant effect of coumadin. It may be far more reasonable to consider tailoring the coumadin dose, thus reducing the risk of bleeding while allowing our patients to continue to use products that might benefit their other health concerns.
Recommended Resources
McGuffin M, Hobbs C, Upton R, Goldberg A (eds.). Botanical Safety Handbook, CRC Press, Boca Raton, 1997.
Brinker F. Herb Contraindications and Drug Interactions, Eclectic Medical Publications, Sandy, Oregon, 1998.
HealthNotes Clinical Essentials, www.HealthNotes.com (CD ROM).
HerbalGram, the Journal of the American Botanical Council, www.herbalgram.org
Michael Traub, ND, is currently president of the American Association of Naturopathic Physicians. He practices in Kailua-Kona, Hawaii, and is on staff at North Hawaii Community Hospital.
