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Herbs and Prescription Drug Interactions
By Shane Hoffman
As Chinese herbs, vitamin and supplement usage become more commonplace, a new and relevant concern emerges. Will all this stuff work together to achieve the desired remedy or effect? Or are there interactions which yield detrimental effects? This question has become more of a concern of late for several reasons
Until very recently, our western system of medicine has not credited complementary therapies with providing any consistent benefit. Attitudes have begun to change markedly beginning with the public outcry at the FDA attempts to regulate supplement, vitamin and herbal products in 1994. The largest public reaction to any legislation ever was the first indication to the medical establishment in this country to the widespread use of complementary medicines. The use of these therapies was quantified in the 1989 study published in the JAMA (Journal of the American Medical Association) . It elucidated by telephone survey that in 1997 Americans made 629 million visits to practitioners of 16 major types of complementary medical practice. Study extrapolations assert that 15 million American adults took a prescription drug while they were also taking some type of complementary remedy. Of that group only 38.5% disclosed this fact to their doctor. The same study further asserts that Americans spent 21.2 billion dollars on complementary care. An amount larger then the out-of-pocket costs for all inpatient hospital visits for all Americans.
This information illustrates a problematic gap in patient care. Patients are taking substances without the informed input of their various medical providers. This point advocates the need for integrated medical practice. Patients who seek care from providers in different types of therapies need to be certain that all of their providers are aware of what they are taking. If the patient is uncertain about the combination, he needs to seek information to make an informed choice. In a complicated case, it might be appropriate for the team of providers to consult with each other. For example, it is not advisable to take gingko biloba prior to surgery. It increases vascular blood flow and could precipitate excessive bleeding in surgery.
We all need to strive to make the most informed choices possible. In this day and age of the media boondoggle, remember that the evening news or the latest book touting a special diet does not consider your particular health picture. The goal of those products is to sell media products; advertising, books and videos. These sources may have the highest intention of helping people, but when it comes to health, that is not enough. As with any choice, consider the source and consider the expertise of the proponent and their knowledge of your complete and particular situation. Patients need to take responsibility for managing health care, diet and lifestyle choices with the benefit of the input of all of their medical providers. These are the people you are paying for their expertise within their specialty.
As a burgeoning area of attention, new studies and information are being reported about possible interactions. Following is a list of some possible interactions for consideration organized alphabetically by drug name. Below is more detailed information on the nature of these interactions organized by drug. Keep in mind when reading this that these are guidelines, and it is imperative to consult a professional herbalist about your specific situation before taking any herbal formulas.
DRUG TYPE HERB (Common name) HERB (Chinese name)
Phenobarbital, etc. Barbituates Valerian -
Cordarone orPacerone(amiodarone hydrochloride) Antiarrhythmia Echinacea (for more then 8 weeks) -
All Anticonvulsants, Antipsychotics Evening Primrose Oil &Borage Oil -
Coumadin(warfarin sodium) Anticoagulant Cnidium Chuan xiong
Coumadin(warfarin sodium) Anticoagulant Salvia Dan Shen
Coumadin(warfarin sodium) Anticoagulant Persica Tao ren
Coumadin(warfarin sodium) Anticoagulant Carthamus Hong hua
Digoxin(lanoxin) Cardiac glycoside Kyushin -
Digoxin(lanoxin) Cardiac glycoside Licorice Gan cao
Digoxin(lanoxin) Cardiac glycoside Plantain -
Digoxin(lanoxin) Cardiac glycoside Uzara root -
Digoxin(lanoxin) Cardiac glycoside Ginseng Ren shen
Digoxin(lanoxin) Cardiac glycoside Hawthorn -
Methotrexate Antimetabolite Echinacea (for more then 8 weeks) -
Nardil(phenelzine sulfate) MAO Inhibitor Ginseng Ren shen
Nizoral(ketoconazole) Antifungal Echinacea (for more then 8 weeks) -
Prozac, Zoloft, Paxil Selective Serotonin Re-uptake Inhibitor St. John's Wort
Spironolactone(aldactone) Diuretic Licorice Gan cao
Synthroid, etc. Thyroid Replacement Therapies Kelp (as Iodine source) -

Echinacea: as an immune system support herb Echinacea might worsen symptoms of autoimmune diseases like multiple sclerosis, lupus, rheumatoid arthritis when used for longer then 8 weeks at a time.
Evening Primrose Oil: usually used to help lower blood cholesterol and moderate symptoms of menopause. It might lower seizure thresholds by interacting with seizure medication and/or schizophrenia medication.
Feverfew: used to treat headaches and migraines. Might reduce blood clotting function, so ought to be avoided in combination with the drugs heparin or Coumadin, blood thinners.
Garlic: used to support the immune system, lower blood cholesterol, and lower blood pressure. Can delay the speed of blood clotting so should also be avoided with the drug Coumadin. For the same reason, also might not be taken with anti-inflammatory medication, like ibuprofen, aspirin or naproxen.
Ginger: used to support digestion or reduce motion sickness. Can delay the speed of blood clotting so should also be avoided with the drug Coumadin. For the same reason, also might not be taken with anti-inflammatory medication, like ibuprofen, aspirin or naproxen.
Gingko Biloba: used to support memory function, increase blood circulation and blood flow. Can delay the speed of blood clotting so should also be avoided with the drug Coumadin. For the same reason, also might not be taken with anti-inflammatory medication, like ibuprofen, aspirin or naproxen. In addition might interfere with anti-depressant medications called MAO inhibitors.
Ginseng: used an an energy and immune support. Ginseng is processed in the liver by a specific enzyme, the cytochrome liver enzyme CYP 3A4, as are many medication, such as, tagamet, allopurinol, MAO inhibitors, many antibiotics and antifungal, cardiovascular medications like the blood thinner Coumadin and the heart medication digitalis, also known as Digoxin and Lanoxin --even alcoholic beverages! Thus taking ginseng with these substances may alter their blood levels resulting in adverse consequences. Check with your pharmacist to see if medicine you take is processed in this way in the body.
St. John's Wort: used to help treat depression. Might increase the neurotransmitter serotonin. For this reason, it might interfere with drugs like Prozac, Zoloft or Paxil which are in the class of drugs called "selective serotonin reuptake inhibitors" or SSRTI's. It might also interfere with the steroidal medications theophylline, cyclosporine and Phenobarbital. Might also reduce the effect of the birth control pill. For warnings about St. John's Wort and HIV anti-virals see this link.
Licorice: as an immune support in treatment of colds or coughs and also to reduce the symptoms of ulcer disease. Licorice can reduce potassium levels in the body. For this reason, it might interfere with the heart drug Digoxin, also known as Lanoxin and or diuretics. Might also increase the effects of topical corticosteroids.
To read about herbs and pregnancy, Click here
Two books (both at the NY Public Library) and several websites consider these issues. One of the best ways to check the most current information is to search the web for the name of drug you are taking. Here are some of the current sources available:
Brinker, Francis J., Herb Contraindications & Drug Interactions: with appendices addressing specific conditions and medicines; Eclectic Institute, Sandy, OR: c1998.
Lininger, Jr.; Schuyler, W. et al, A-Z Guide to Drug Herb Interactions: how to improve your health and avoid problems when using common medications and natural supplements together; Prima Health, Rocklin, CA; c1998.
Other Web Links:
Holistic Online -Herbal Medicine
Interaction Report.Org