An increasing number of American adults now take herbs or nutritional supplements for a wide range of ailments, including arthritis, depression and nausea.

Problem: Unlike prescription drugs, herbal supplements are not regulated by the FDA, so there are no labeling requirements regarding potential interactions with prescription or over-the-counter (OTC) drugs.

Whether they are used in capsules, extracts, liquid, cream or tea, many herbal products can be harmful when combined with prescription or OTC medication.

What happens: Some herbs can interact with medications by affecting their absorption, metabolism or by other mechanisms. As a result, drug levels may become too high or too low.

Catherine Ulbricht, PharmD, is a pharmacist at Massachusetts General Hospital and one of the country's leading experts on herb-drug interactions. Her advice on commonly used herbs. .."


Cayenne is also known as chili or red pepper. Cayenne's active component, capsaicin, which is used as a spice in food, is commonly used as a pain reliever in prescription medicine, often for osteoarthritis, rheumatoid arthritis and diabetic neuropathy (nerve pain resulting from diabetes).

Possible interactions: When combined with aspirin, Ibuprofen  (Advil) or any other nonsteroidal anti-inflammatory drug (NSAID), cayenne may increase these drugs' side effects. especially gastrointestinal (GI) upset. In some people, cayenne also may enhance the pain-relieving action of NSAIDs.

Like NSAIDs, cayenne can have a blood-thinning effect, increasing the risk for bleeding.

*Check with your doctor or pharmacist before taking any herbal product.

(When used topically, this risk is lessened because lower doses of cayenne are absorbed.) Do not use cayenne if you take a monoamine oxidase (MAO) inhibitor antidepressant, such as Phenelzine (Nardil).

Caution: Avoid getting cayenne (in any form) in your eyes, nose, etc., where it can cause burning or stinging.


Ginger is a popular antidote for nausea and/ or vomiting. Research suggests that ginger also may help prevent blood dotting and reduce blood sugar levels.

Possible interactions: If you take an NSA1D or antiplatelet drug, such as Clopidogrel (Plavix), ginger may further increase bleeding risk.

Caution: Although there's strong evidence that it is particularly effective for nausea and/or vomiting in pregnant women, high-dose supplemental ginger (more than 1 g daily) is not recommended during pregnancy because of possible fetal damage and/or increased bleeding risk. Because of the lack of long-term studies on ginger, consult your doctor before taking it for an extended period of time.

Green Tea

As scientific evidence has revealed the disease-fighting benefits of antioxidant-rich green tea, an increasing number of Americans have begun drinking it—or, in some cases, taking it in capsules or extracts. Although new research questions the health benefits of green tea, some studies have found that it may help prevent cancer, especially malignancies of the GI tract. breast and lung. More investigation is needed to con-firm these findings. To read more about clinical trials on green tea, go to the National Institutes of Health's Website,

Possible interactions: Most forms of green tea contain caffeine, which may intensify the effect of any medication that increases blood pressure and/or heart rate, such as the decongestant pseudoephedrine (Sudafed). Decaffeinated green tea is available, but this form still contains some caffeine and may not have the same health benefits.

Caution: People with arrhythmia (abnormal heart rhythm) should consume no more than moderate amounts of green tea, determined by their personal sensitivity to caffeine.


Licorice contains a compound known as glycyrrhizin, which has antiviral properties. For this reason, licorice is often used to treat the common cold and herpes infections (including cold sexes). However, some studies have shown that topical licorice cream does not help genital herpes.

Possible interactions: Licorice can interact with diuretics, such as Chlorothiazide (Diuril) and furosemide (Lasix), and any medication that affects hormone levels, such as birth control pills.

Caution: It also may increase blood pressure and bleeding risk.

Milk Thistle

This popular herb is used for liver problems, including cirrhosis and hepatitis. These benefits are well documented by research.

Possible interactions: Milk thistle may interfere with how the liver breaks down certain drugs, such as antibiotics and antifungals. Milk thistle also may interact with the anticonvulsant phenytoin (Dilantin). The herb may lower blood sugar and cause heartburn, nausea and vomit-ing or other GI upset.

Caution: If you take diabetes medication, do not use milk thistle unless you are supervised by a health-care professional.

St. John’s Wort

St. John's won is commonly used for depression. Several studies show that it may work as well as a prescription antidepressant, such as paroxetine (Paxil), for mild to moderate depressive disorders. More research is needed before St. John's wort can be recommended for severe depression.

Possible interactions: St. John's won may interact with drugs that are broken down by the liver, including birth control pills, the blood thinner warfarin (Coumadin) and migraine medications. People who take St. John's won may experience stomach upset, fatigue, sexual dysfunction, dizziness or headaches.

Caution: St. John's wort should not be taken with prescription antidepressant medication.

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