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Herbal Remedies Can Interfere With Your Medications

Always Discuss Any Herbal Remedies You Are Taking With Your Doctor

By Rosalyn Carson-DeWitt, MD

Updated February 26, 2009

(LifeWire) - Herbs have been used throughout the ages to treat medical conditions and promote health, and in recent decades they have become increasingly popular in the United States. In 1990, only 2.5% of Americans reported using herbal remedies; this figure rose to 12% by 1997 and to 10 to 19% by 2002. In 2004, 25% of American adults reported that they had used herbal products within the previous year.

Many people regard such products as safe and "natural." Although herbs are found in nature, they contain chemically active compounds that have an effect on the user. Furthermore, they sometimes interact with prescription medications. Research from 1997 showed that about 15 million people were using both herbal and prescription preparations. Only about half realized that it was important to tell doctors and other healthcare providers about their use of herbal health products.

How Herbal Remedies Can Interact With Prescription Drugs

There are three ways they can interact:

Synergistic or similar effects: The two have a similar effect; when taken together, they can cause too much of that effect -- and may increase the risk of side effects.

Antagonistic or opposite effects: The two have opposite effects; when taken together, each interferes with the other's effectiveness.

Decreased bioavailability: The herbal remedy may diminish the prescription drug's availability to the body -- and so hinder its intended therapeutic function.

Herbal Remedies and Possible Drug Interaction

How some herbal remedies might interact with prescription medications:

-Devil's Claw (used for back pain)
Might increase bleeding and bruising when used with blood thinners.

-Dong Quai (used for menstrual and menopausal symptoms)
Might increase bleeding and bruising when used with blood thinners.

-Evening Primrose (used for premenstrual symptoms and for eczema)
Might decrease the effectiveness of seizure medications, increasing the risk of seizure.

-Feverfew (used for fevers, headache, toothache, menstrual symptoms, childbirth, arthritis, psoriasis, asthma, allergies)
Might increase bleeding and bruising when used with blood thinners. Also, may increase heart rate and blood pressure when used with migraine medications.

-Garlic (used for heart disease, high blood pressure, high cholesterol, cancer prevention)
Might increase bleeding and bruising when used with blood thinners; cause low blood sugar when used with diabetic drugs; and decrease the effectiveness of certain HIV drugs.

-Ginger (used for nausea, joint pain, muscle pain)
Might increase bleeding and bruising when used with blood thinners.

-Ginkgo (used for memory, sexual problems, asthma, ringing in the ears)
Might increase bleeding and bruising when used with blood thinners; decrease the effectiveness of seizure medications, increasing the risk of seizure; and increase the risk of side effects, such as headache, trembling and mania, when used with monoamine oxidase inhibitor (MAOI) antidepressants.

-Ginseng (used for general health, energy, sexual problems, symptoms of menopause, blood sugar control and high blood pressure)
Might increase bleeding and bruising when used with blood thinners; cause low blood sugar when used with diabetic drugs; and increase the risk of side effects, such as headache, trembling and mania, when used with MAOI antidepressants.

-Goldenseal (used for skin problems, mouth sores, colds, diarrhea, cancer)
Might increase the risk of blood clots when used with blood thinners.

-Licorice (used to treat ulcers, sore throat, viral infections)
Might interfere with effectiveness of high blood pressure medications and heart rhythm drugs; might exaggerate the effects of diuretic medications, resulting in an imbalance of potassium, sodium and water in the blood.

-Milk Thistle (used to treat liver and gallbladder problems, cholesterol, cancer)
Mght cause low blood sugar when used with diabetic drugs; might decrease the effectiveness of certain HIV drugs.

-Red Clover (used for menopause, high cholesterol, osteoporosis, prostate problems)
Might decrease the effectiveness of birth control pills or increase bleeding and bruising when used with blood thinners.

-St. John's Wort (used for depression, anxiety, sleep problems)

Might decrease:

  • the effectiveness of anti-anxiety drugs, resulting in increased anxiety and sleepiness
  • the effectiveness of immunosuppressant or anti-rejection drugs
  • the effectiveness of heart failure or heart rhythm drugs
  • the effectiveness of certain HIV drugs

Might increase:

  • the risk of high blood pressure with MAOI antidepressants
  • the effect of and side effects from selective serotonin reuptake inhibitor (SSRI) antidepressants.
  • the risk of blood clots when used with blood thinners
  • metabolism of tamoxifen, an anti-cancer drug used for breast cancer

-Valerian (used for sleep problems, anxiety, headache, depression)
Might increase the sedative or depressant effect of alcohol, sedatives, tranquilizers, and anesthesia drugs.

Sources:

Bent, Stephen, and Richard Ko. "Commonly Used Herbal Medicines in the United States: A Review." American Journal of Medicine 116:7(2004):478-85. 22 Jan. 2009. <http://www.amjmed.com/article/S0002-9343(03)00799-X/abstract>(subscription).



Ernst, E., and M.H. Pittler. "Herbal Medicine." Medical Clinics of North America 86:1(2002): 149-61. 22 Jan. 2009 <http://www.medical.theclinics.com/article/PIIS0025712503000774/fulltext> (subscription).



Gardiner, Paula, and Tieraona Low Dog. "Prescribing Botanicals." Rakel: Integrative Medicine, 2nd Ed. Ed. David Rakel. Philadelphia: Saunders Elsevier, 2007.



"Herbs at a Glance." nccam.nih.gov. Jan. 2009. National Center for Complementary and Alternative Medicine, National Institutes of Health. 22 Jan. 2009. <http://nccam.nih.gov/health/herbsataglance.htm>.



"Medicinal Herbs and Nutraceuticals." merck.com. From Merck Manual of Medical Information, 2nd ed. Ed. Robert S. Porter. Whitehouse Station, NJ: Merck Research Laboratories, 2004-08. 22 Jan. 2009. <http://www.merck.com/mmhe/sec02/ch019/ch019a.html>.



Meletis, Chris D. "A Selective Look at Drug-Natural Medicine Interactions." Rakel: Integrative Medicine, 2nd ed. Ed. David Rakel. Philadelphia: Saunders Elsevier, 2007.



Taylor, David McD., et al. "Potential Interactions Between Prescription Drugs and Complementary and Alternative Medicines Among Patients in the Emergency Department." Pharmacotherapy 26:5(2006): 634-40. <http://www.atypon-link.com/PPI/doi/abs/10.1592/phco.26.5.634> subscription


LifeWire, a part of The New York Times Company, provides original and syndicated online lifestyle content. Rosalyn Carson-DeWitt, MD, works as a medical writer, editor, and consultant in Durham, NC. She served as editor-in-chief for two multi-volume MacMillan encyclopedias:  The Encyclopedia of Drugs, Alcohol, and Addictive Behavior and Drugs, Alcohol and Tobacco: Learning About Addictive Behavior. She worked on the 18th edition of the Merck Manual of Diagnosis and Therapy, and has written thousands of print and online articles for healthcare providers and consumers.

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