Think your supplement is safe? Think again

Category: Tips Ubat

Herb-drug interactions that patients need to know

What is a Herbal Supplement?

Herbal supplements are sold in many different forms – dried leaves for teas, powdered, as capsules or tablets, or in solution.

The use of herbal supplements has a long history – dating back thousands of years. Examples of important medicines extracted from botanicals include reserpinemorphinepenicillin, and vinca alkaloid anti-cancer drugs.

Today, herbal supplements and nutraceuticals can be purchased over-the-counter (OTC) and may be labeled “all-natural”, 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.

Patients need to understand that herbal medications are not completely safe, and that these preparations, when taken with other drugs, can alter the way that the drug is processed and excreted by the body, enhance a drug’s side effects, or block the intended therapeutic effect of the drug.

  1. Coenzyme Q10

Coenzyme Q10 protects the heart from damage from cancer medications. The use of coenzyme Q10 with warfarin decreases its blood thinning effects and may increase the risk for a blood clot.

  1. John’s Wort supplements

Supplements containing St. John’s Wort are commonly used to treat symptoms of depression. This should not be used concomitantly with other antidepressants, migraine medications, dextromethorphan, warfarin, birth control pills, and certain antiretroviral medications due to seriousness of drug interactions.

  1. Ginseng

Ginseng is commonly used to improve the body’s resistance and vitality. There are four known types of ginseng, namely American, Korean, Siberian and Brazillian. Of these, “American ginseng” is known to decrease the effects of warfarin and should not be used together with other anticoagulants, though this cannot be conclusively said for the other three types. Different type of Ginseng have different interaction with Warfarin. Ginseng also has an effect in blood pressure and diabetic medications like insulin or oral hypoglycemics.

  1. Ginkgo biloba

Ginkgo biloba is used to enhance memory, and in improving symptoms of Alzheimer’s and Parkinson’s diseases. It can decrease effects of certain HIV medications, and alter the actions of drugs metabolized by the liver.

  1. Cranberry

Even the simple cranberry can have drug interactions.

Cranberries are a fruit chock 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; but it is not helpful to cure a UTI.

Cranberry may exert an increased effect on blood thinners (anticoagulants) 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.

  1. 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 bruising or bleeding. If you take drugs or herbs that 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.

  1. 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 moderately 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.

  1. 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, as a stimulant, and to lessen belly fat, 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, which can increase blood clotting. Large amounts of vitamin K may interfere with the activity of some blood thinners.

A substantial decrease in the INR (a measure of blood clotting) 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 as it can interfere with the blood-thinning capabilities of warfarin.

  1. 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.

It is known to inhibit thromboxane synthetase, which can prolong bleeding time and may cause interactions with anticoagulants like warfarinaspirin, or other blood thinners.


There are many other herbs that can interact with medications.

“It is important that patients consult first with a physician before taking any herbal supplements, or inform their physician if they are taking herbal preparations if they are prescribed with medications.” 

Thank you for reading 🙂