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How safe are herbal medicines?

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Herbal medicinal sales increased nearly 60% in 1997, accounting for $3.24 billion in sales (as reported in a research study in the “Archives of Internal Medicine”). In 1997, 60 million Americans stated that they had used herbs in the previous year, yet 70% did not reveal their herbal use to their physicians or pharmacists. Sale of herbal medicines is big business, yet consumers must be aware of the adverse consequences, as well as the benefits.

Here is a list of commonly used herbal medicines, drugs with known potential drug-herb interactions and drugs that can have enhanced effects if taken at the same time as an herb.

* Echinacea if used beyond 8 weeks could cause hepato-toxicity and should not be used with other known hepato-toxic drugs such as anabolic steroids, amiodarone, methotrexate, ketoconazole.
* Feverfew is used for migraine headaches, yet its usefulness may be negated with nonsteroidal anti-inflammatory drugs.
* Feverfew, garlic, ginko, ginger and ginseng may alter bleeding time and should not be taken concomitantly with warfarin.
* Valenan, used for insomnia, should not be used with barbiturates because excessive sedation may occur.
* Evening primrose oil and borage should not be used with anti-convulsants because they may lower seizure threshold.
* Immunostimulants (echinacea and zinc) should not be given with immunosuppressants (corticosteroids and cyclosporine).
* Tannic acid present in some herbs (e.g., St. John’s wort and saw palmetto) may inhibit absorption of iron.
* Kelp, as a source of iodine, may interfere with thyroid replacement therapies.
* Licorice can offset the pharmacological effect of spironolactone.
* Karela and Ginseng may affect blood glucose levels and should not be used in patients with diabetes.

Herbs can be helpful and do provide pharmacologic action, but careful consideration of other medications and dosage of herbs must be made before use.

Posted on 17 Apr 2000

Nedra Christensen
Utah State University Extension Dietician

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