Taking herbal remedies is tempting. Testimonials abound from people who have solved their medical problems with "safe, natural" and over-the-counter pills. And there's plenty of literature – in print, on the Internet and on TV - from companies that manufacture and sell these products. But informed consumers need to know that there are very few valid medical studies on herbal remedies, their safety, effectiveness or mechanisms of action.

Although herbs seem harmless (after all, we use them to season our food), some can be potentially dangerous, especially to anyone taking medication for a heart problem. Unlike conventional medications, herbal supplements do not undergo rigorous scientific study using randomized, controlled clinical trials that are designed to measure objective "end points." Serious, even fatal, interactions have been reported between cardiac medicines and some supplements. Cleveland Clinic cardiologists warn that anyone who takes digoxin, diuretics, hypoglycemics, nonsteroidal anti-inflammatory drugs, spironolactone, or warfarin should not use supplements, without first checking with their doctor: (See chart.)

Cleveland clinic cardiologists warn cardiac patients against taking these herbal remedies

If you take digoxin, diuretics, hypoglycemics, nonsteroidal anti-inflammatory drugs, spironolactone, or warfarin, do not use the following supplements, without first checking with your doctor.

Name of remedyUsesRisks
Ephedra (Ephedra sinica, also called Ma-Huang)To treat coughs and obesityDangerous and life-threatening increases in heart rate and blood pressure. Has potentially fatal interactions with many cardiac medicines.
Garlic (Allium sativum)To lower cholesterol; to prevent and treat colds and certain infections.Increases the risk of bleeding when taken with blood-thinning drugs.
Ginkgo (Ginkgo biloba)To improve memory, circulation, and mental function as well as to prevent altitude sicknessIncreases the risk of excess bleeding when taken with blood-thinning drugs.
Goldenseal (Hydrastis canadensis)To alleviate constipation. Acts as an anti-inflammatoryMay decrease or increase blood pressure. Berberine (ingredient of goldenseal) has also been associated with heart rhythm abnormalities. Increases the risk of bleeding when taken with blood-thinning drugs.
Hawthorn (Crataegus species)To alleviate congestive heart failure and high blood pressureIncreases the risk of bleeding when taken with blood-thinning drugs.
Licorice root (Glycyrrhiza glabra)To treat coughs, cirrhosis, and stomach ulcersMay increase blood pressure and has been associated with heart rhythm abnormalities.

Many of the drug interactions result from the fact that the herbs contain naturally-occurring compounds called coumarins that are anticoagulants. (In fact, warfarin is a coumarin, as its trade name, Coumadin, implies.) The additional anticoagulants in the herb interfere with the workings of the prescription drugs, says Mike Militello, PharmD, cardiology clinical pharmacist at Cleveland Clinic. For example, dong quai (Angelica sinensis) contains coumarin components, "but there are many others as well," Dr. Militello notes.

High levels of vitamin K are also a problem. "Vitamin K actually reverses the effects of warfarin," Dr. Militello notes. He urges anyone taking warfarin to avoid excessive amounts of alfalfa, as well as agrimony, plantain, and stinging nettle. (Since vitamin K is also found in green, leafy vegetables, they should also be avoided.)

Other supplements are known to cause heart problems, whether or not the consumer is also taking heart medications. These include:

  • Aloe - used internally to relieve constipation and externally to soothe irritated skin and burns. When taken internally, aloe can cause abnormal heart rhythms with prolonged used.
  • Arnica ( Arnica montana) - applied externally to reduce pain from bruising, aches and sprains, and to relieve constipation. Arnica is potentially toxic to the heart and can raise blood pressure if taken internally.
  • Black cohosh ( Cimicifuga racemosa) - used to relieve menopausal symptoms. Can cause lowered blood pressure when taken at high doses.
  • Feverfew ( Tanacetum parthenium) - believed to prevent and treat migraines, arthritis and allergies. Feverfew can interfere with blood clotting when taken internally.
  • Ginger - purported to alleviate nausea and motion sickness, lower blood cholesterol, decrease platelet aggregation, and as a digestive aid and antioxidant. Ginger can interfere with blood clotting and increase the risk of bleeding when taken with blood-thinners. High dose has been associated with abnormal heart rhythm and blood pressure changes.
  • Ginseng ( Panax ginseng) - supposed to slow aging, increase mental and physical capacity, increase sexual performance, and boost immunity. It should not be taken by people with hypertension. Ginseng can interfere with blood clotting and increase risk of bleeding when taken with blood-thinners.
  • Stinging nettle ( Urtica dioica) - thought to fight urinary tract infections, kidney and bladder stones, and rheumatism. It is used externally to control dandruff. Nettle should not be taken by people with fluid retention caused by reduced heart or kidney function.

Unlike prescription medications, herbal remedies are classified as dietary supplements and therefore bypass the tight Food and Drug Administration scrutiny that prescription medications must undergo. In fact, the Dietary Supplement Health Education Act of October 1994 doesn't require manufacturers of herbal products to prove that their products are either safe or effective.

To make matters worse, computer software used by pharmacists to alert them to potentially dangerous drug interactions don't recognize adverse interactions with herbal products. If the lure of, say, improved memory or relief from arthritis pain seems strong, do your heart a favor and talk to your doctor before trying a "safe" herbal remedy.

Reviewed by Mandy Leonard, Pharm.D., Manager, Drug Information Center, Cleveland Clinic Foundation

Reviewed: 12/13

Reviewed by a Cleveland Clinic medical professional.

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