About 60 million Americans say they use dietary supplements or herbal remedies. Some of that number are also taking prescription medicines.

Yet certain herbs and supplements can interact with medications in a negative manner. Worse, as the number of supplements grows, so do the possible interactions.

Surgery typically involves medications such as anesthesia, as well as an incision. So the use of natural supplements and remedies can affect the surgery and its outcome.

For this reason, it is critically important that you tell your doctor about any herbal medications, supplements, or megavitamins you may be taking. If you need emergency surgery, it's important that a relative or friend be able to give the emergency surgeon the same information.

Widespread problem

Interactions of herbs and supplements with medications used during surgery--including anesthetics, epinephrine, muscle relaxants, and anti-arrhythmics--have become commonplace. As a defense against complications, your doctor, the anesthesiologist, and the nursing staff may ask you about any supplements and herbs you take.

You may be asked to stop taking dietary supplements and herbs two to three weeks before surgery. This is the safest course of action, says the American Society of Anesthesiologists. For emergency surgery, however, you won't have the opportunity to stop the supplements ahead of time.

Here is a short explanation of complications associated with some of the more common herbal remedies and supplements.

Ephedra

Possible complications: heart attack and stroke

Ephedra is available in only limited dosage in this country because it can cause heart attacks and stroke. Ephedra raises blood pressure and increases heart rate. It can cause headache, nausea, rapid heart rate, and the inability to empty your bladder completely. On the beneficial side, it increases blood flow to the heart, brain, and muscles and can open constricted bronchial tubes during an asthma attack.

Garlic

Possible complications: bleeding during and immediately following surgery

In large doses, garlic may lower blood pressure and interfere with blood clotting. This increases the risk for serious bleeding during surgery. Garlic can increase the effect of warfarin, a drug used to prevent blood clotting. In combination with chlorpropamide, garlic may cause low blood sugar

Ginkgo

Possible complications: bleeding during and immediately following surgery

Ginkgo interferes with blood clotting and also dilates blood vessels. This may lead to increased bleeding during surgery and just after surgery. Ginkgo may also lead to abnormal bleeding when used in conjunction with the prescription drug warfarin or with aspirin.

Ginseng

Possible complications: bleeding during and immediately following surgery

Ginseng can interfere with normal blood clotting. In addition, it has significant stimulatory effects on the central nervous system. It can cause headaches, nervousness, and sleep abnormalities or insomnia. Ginseng can cause hypoglycemia. Ginseng interferes with some prescription drugs. It enhances the effect of warfarin and may result in unwanted and dangerous bleeding. When taken with phenelzine, it can cause insomnia and psychological effects, particularly mania from hyperstimulation.

Kava

Possible complications: may increase the sedative effect of anesthesia

In the South Pacific islands, Kava is used socially for relaxation. It can increase the effect of alcohol, sedatives, or anesthesia. Kava has also been associated with causing liver damage, with some fatalities. The exact mechanism of action is still being studied. Because kava interferes with cytochromes, it has the potential to interact with a fairly large number of drugs. However, no specific studies are available at this time. Kava has been implicated in several cases of liver failure.

Saint-John's-wort

Possible complications: may cause acute rejection of a transplanted organ by interfering with anti-rejection medications; rejection may begin within 24 hours of taking Saint-John's-wort

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