18 Herbal Supplements with Risky Drug Interactions

What is a Herbal Supplement?

The use of herbal supplements has a long history - dating back thousands of years. Examples of important medicines extracted from botanicals include reserpine, morphine, penicillin, and vinca alkaloid anti-cancer drugs. Today, herbal supplements and nutraceuticals can be purchased over-the-counter (OTC), but that does not always mean they are safe. While these products are intended to boost health, and may make claims to that effect, robust clinical studies may be lacking. Herbal supplements are sold in many different forms - dried leaves for teas, powdered, as capsules or tablets, or in solution. Almost 20 percent of Americans currently take some type of herbal or non-herbal supplement.

Does the FDA Regulate Herbal Products?

Herbal supplements are not subject to review by the FDA and their use can be risky. Consumers need to understand that even though the label may say "natural", these products are not always safe. It is best to have your pharmacist or doctor check for drug interactions prior to using any herbal supplement. Herbal products can frequently have drug interactions with prescription medications. The FDA does not apply the same effectiveness and safety studies used for prescription drugs to herbals and their manufacturers. The FDA can and does seize and remove from the market tainted, contaminated or unsafe dietary supplements when they are aware of problems.

Herbs Are 'All Natural' - Why Worry About Drug Interactions?

Even though herbal supplements may be from plant or herb sources, the active ingredients can still be potent chemicals. Because of this, herbal supplements can have drug interactions, even with each other or with food or alcohol. Unfortunately, these products are not labeled with safety warnings, and it is difficult for a consumer to know if an interaction may occur. Herbal interactions with prescriptions can interfere with how the drug may be broken down in the body, enhance side effects of prescription medications, or block the intended therapeutic effect of a drug. You can search for herbal supplement-drug interactions here, and always check with your doctor or pharmacist.

Black Cohosh

Black cohosh is a shrub-like plant found in North America. Black cohosh is often used for menopausal disorders ("hot flashes"), painful menstruation, uterine spasms, and vaginitis. There is concern that black cohosh might be toxic to the liver and may enhance liver toxicity with certain medications that also cause liver toxicity - (for example, atorvastatin, acetaminophen, alcohol). Drugs broken down by certain liver enzymes may accumulate in the body and lead to toxicity if used with black cohosh. Drug interactions are complicated and numerous, so have your medications screened by your pharmacist to review for black cohosh drug interactions.
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Coenzyme Q10

CoenzymeQ10, also known as ubiquinone or CoQ10, is found naturally in the heart, kidney, liver and pancrease, but aging and smoking can deplete these natural stores. CoQ10 is claimed to help heart damage caused by certain cancer medicines and for breast cancer, gum disease, or muscular dystrophy. Use of CoQ10 with anticoagulant drugs like warfarin may decrease the blood thinning effects of the anticoagulant and increase the risk for a clot. If you take a blood thinner, check with your doctor before starting CoQ-10. You may need to have your blood clotting tests checked more frequently and may need a change in your anticoagulant dose.

Cranberry

Cranberries are a fruit full of vitamin C, and some people drink cranberry juice to help prevent urinary tract infections (UTI). Although data is conflicting, some studies have shown cranberry can reduce recurrent UTIs in pregnant women, the elderly and hospitalized patients. Even the simple cranberry can have drug interactions. Cranberry may exert an increased effect on blood thinners (anticogulants) like warfarin and lead to bruising or bleeding. If you take an oral blood thinner, check with your doctor before consuming unusual amounts of cranberry or cranberry juice. You may need to have your International Normalized Ratio (INR) or other blood clotting lab test checked more frequently.

Echinacea

Echinacea is also known as the American Cone Flower, Black Susan, or Purple Coneflower. Echinacea has been used to stimulate the bodies immune defense system, and is most commonly used in the treatment of the common cold. Most echinacea drug interactions are minor. Echinacea might slow the breakdown (metabolism) of caffeine in your body, and could lead to side effects like jitteriness, headache, or insomnia. Echinacea may also change how the body metabolizes many drugs that are affected by the CYP450 system; these are complicated interactions that can lead to side effects or reduced effectiveness of your medicine, so always check with your pharmacist.

Evening Primrose Oil

Evening primrose is a flowering plant known by other names such as Oenothera biennis, scabish, or king's cureall. Evening primrose oil provides fatty acids used by the body for growth. Evening primrose oil contains gammalinoleic acid that may slow blood clotting and increase the likelihood of brusing or bleeding. If you take drugs or herbs that have may have blood thinner effects, check with your health care provider before using evening primrose oil. Use of evening primrose oil may increase the risk for seizures if you take anti-seizure medications or phenothiazine drugs. You can check for other evening primrose oil drug interactions here.

Valerian

Valerian has been used to treat insomnia and anxiety, although evidence is conflicting. Germany's Commission E, the authorities that evaluate the use of herbal products in Germany, has approved valerian as an effective mild sedative. There are over 500 possible drug interactions with valerian, so a drug interaction screen is important when using valerian. Speak with your doctor before combining valerian with muscle relaxants, other sleep or anxiety medicines, pain medicines, antidepressants, or other medicines that cause drowsiness. These drugs may increase drowsiness and dizziness while you are taking valerian.

St. John's Wort

St. John’s Wort is a popular herbal supplement widely used to help with symptoms of depression. Drug interactions with St. John's Wort can be numerous and dangerous. Due to the seriousness of many drug interactions, you should consult with your health care provider before using St. John's Wort. Do not combine St. John's Wort with these medications: SSRIs, TCAs, MAO Inhibitors, nefazodone, triptans for migraine, dextromethorphan, warfarin, birth control pills, certain HIV medications, and many other drugs. Check with your doctor or pharmacist for a drug interaction screen with St. John's Wort if you also take prescription, OTC, vitamin or other herbal medications.

Saw Palmetto

Use of saw palmetto is popular for benign prostatic hypertrophy (BPH), a noncancerous prostate gland enlargement. Evidence suggests that saw palmetto may be effective for mild-to-moderate BPH. Saw palmetto should be avoided with other agents used to treat BPH, such as finasteride (Proscar), unless directed by your doctor. Saw palmetto may also slow blood clotting and may increase the risk for bruising or bleeding if used with certain blood thinners like warfarin. If saw palmetto is combined with estrogens or oral contraceptives, the effectiveness of the hormonal therapies could be reduced. Check with your doctor or pharmacist for a drug interaction screen.

Melatonin

Melatonin is a natural hormone that helps to regulate the sleep-wake cycle. It is thought that melatonin tablets may be helpful for insomnia, jet lag and shift work sleep disorders. Melatonin causes drowsiness; use should be avoided with alcohol and other sedating medicines (for example, benzodiazepines sedatives and hypnotics, some antihistamines, opioid analgesics or muscle relaxers. Other herbs that can also lead to drowsiness include 5-HTP, kava, and St. John’s Wort. Melatonin may also increase blood sugar and interfere with diabetes medications. As with many herbal products, blood clotting may be affected with use of melatonin with anticoagulants.

Kava

Kava, native to the South Pacific, is a member of the pepper family. Kava has been used to improve sleep, decrease anxiety, and tame nervousness, stress, and restlessness. There are hundreds of drug interactions with kava. Kava should not be used with alcohol, other drugs or herbs that can also cause liver toxicity. The use of buprenorphine (Buprenex) with kava can lead to serious side effects such as respiratory distress or coma. Call your doctor immediately if you have fever, joint pain, bleeding, skin rash/itch, appetite loss, fatigue, nausea/vomiting, stomach pain, dark colored urine, light colored stools, and/or yellowing of the skin/eyes; these may be signs of liver toxicity.

Ginseng

Ginseng has been used in Asian countries for its therapeutic effects for centuries. Today, ginseng use is reported to improve the body's resistance to stress and increase vitality, among other uses. There are many different origins of ginseng, and many types of drug interactions. Long-term use of American ginseng may decrease the effectiveness of warfarin, a blood thinner, and increase the risk for a clot. In general, ginseng should not be used with anticoagulants. Ironically, ginseng also has blood thinner effects itself, and may lead to bleeding. Ginseng may also affect blood pressure treatments and diabetic medications like insulin or oral hypoglycemics. Be sure to check with your pharmacist or doctor.

Yohimbe

Yohimbe is the name of an evergreen tree that is found in some African countries. The bark of yohimbe contains a chemical called yohimbine, which can dilate blood vessels and is often promoted for erectile dysfunction (ED) or sexual problems caused by selective serotonin reuptake inhibitors (SSRIs). At least 14 days should elapse between discontinuation of MAOI therapy and initiation of treatment with yohimbine. Therapy with yohimbine is generally not recommended in patients with hypertension, angina pectoris, or heart disease because it has a stimulatory effect and can lead to high blood pressure and a rapid heart rate. You can check other interactions here.

Feverfew

Feverfew is a member of the daisy family. Feverfew is often used as an herbal remedy to prevent migraine headaches and associated nausea-vomiting; however, the evidence is not conclusive. Feverfew may increase the risk of bleeding, especially in people with blood-clotting disorders or using blood thinners to help prevent clots, for example aspirin, warfarin, heparin, Plavix (clopidogrel), Pradaxa (dabigitran), Xarelto (rivaroxaban) or low molecular weight heparins like enoxaparin or dalteparin. Check with your health care provider before using feverfew; you can check for other drug interactions with feverfew here.

Ginkgo Biloba

The use of ginkgo extract dates back centuries in traditional Chinese medicine. Ginkgo has been used for symptoms of Alzheimer's dementia, Parkinson's disease, and to aid in general memory suppport, among other uses. Ginkgo may decrease antiviral effects of drugs used in HIV, such as efavirenz or indinavir. Ginkgo can also alter the actions of medicines metabolized through the liver; the list is extensive but includes agents such as omeprazole (Prilosec OTC), fluvastatin (Lescol), and donepezil (Aricept). Avoid ginkgo in patients who take seizure medications, blood thinners or diabetes drugs. Ginkgo interacts with close to 500 drugs; have a pharmacist check for interactions before use.

Goldenseal

Goldenseal is a flowering herb that grows in the northeast U.S. Common uses for goldenseal include skin infections, for cold and flu, and to treat diarrhea, but evidence is weak for these uses. There are over 60 possible drug interactions with goldenseal. Two of the more serious interactions occur with certain antipsychotic drugs - using pimozide or thioridazine with goldenseal is not recommended, as antipsychotic blood levels may rise leading to an irregular heart rhythm. Goldenseal may affect liver enzymes that can alter blood levels of certain drugs; always have your pharmacist run a drug interaction screen on all of your medicines, OTC drugs, or herbs.

Garlic

Garlic is a commonly used flavoring agent, food product and herbal supplement. There are many conditions garlic has been used for - to reduce cholesterol and triglycerides, to prevent cancer, to lower blood sugar levels, and to reduce menstrual pain, among other uses. Garlic has been reported to affect blood clotting and blood sugar levels and may affect people who take blood thinning agents like aspirin, warfarin, or clopidogrel (Plavix). Use of garlic supplements with HIV protease inhibitors (PI) may decrease the PI blood levels. There are other possible garlic interactions, so be sure to review all possible drug interactions with garlic and speak with your healthcare provider.

Green Tea

Green tea is a popular drink that originated in China and has been promoted for stomach disorders, to lower cholesterol, as an anti-cancer antioxidant, and as a stimulant, among other uses. In the U.S., it has gained recent popularity due to claims it can boost metabolism and aid in weight loss. Dried green tea leaves contain vitamin K, and large amounts may interfere with the activity of some blood thinners. A substantial decrease in the INR has been reported in a patient treated with warfarin after he began consuming large quantities (1/2 to 1 gallon daily) of green tea. Patients treated with warfarin should probably avoid large amounts of green tea.

Ginger

Ginger is a commonly used flavoring agent, food product, and herbal supplement. Ginger has been used in the treatment and prevention of motion sickness, vertigo, to increase appetite, and to reduce stomach acidity. Ginger has also been used by some women under medical supervision to reduce severe nausea and vomiting in pregnancy. Drug interactions with ginger are not well documented; however, it is known to inhibit thromboxane synthetase, which can prolong bleeding time and may cause interactions with anticoagulants like warfarin, aspirin, or other blood thinners. Check other possible ginger-drug interactions here.

How Should I Handle Possible Herbal-Drug Interactions?

It is important to remember that the best way to handle any possible drug interaction is to predict it and prevent it. In order to do that, you need to be proactive in checking for possible drug interactions yourself in addition to asking your health care provider to screen for interactions. Tell your doctor or pharmacist about all the medications you take, including prescription drugs, vitamins, OTCs, and herbal supplements. Be sure a drug interaction screen is conducted each time you start or stop a medication. Consult your doctor about any symptoms you are experiencing and discuss the herbal product prior to its use.

What if I Find Out My Prescriptions Drugs Have an Herbal Interaction?

Advice from your health care provider is your best option in preventing serious health effects from any drug interaction. Remember that herbal supplements are not subject to FDA oversight and have not usually been tested in clinical studies to prove their effectiveness or safety. Contact your health care provider if you discover that a possible drug interaction may occur between medications and herbal products that you use. Do not stop taking your medication unless directed to do so by your doctor. The interaction may be insignificant and no change may be needed - on the other hand - the interaction could be serious and the herbal supplement may need to be discontinued.

Finished: 18 Herbal Supplements with Risky Drug Interactions

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Sources

  • Miller LG. Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions. Arch Intern Med 1998:158;2200-11.
  • Richards JS. Overview of Herbal Supplements. Elite Continuing Education CE 2013. p.46-62.
  • Drugs.com. Natural Products Consumer Database. Dec. 2013. Wolters-Kluwer Health.
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