Herb and Drug Interactions, New Study Findings
True or false: it's always safe to take herbal remedies and nutritional supplements if you are taking any over-the-counter or prescription drugs. Even if you know the correct answer (it's false), it's important to know about herb and drug interactions and which combinations carry potential risks.
Some herb and drug combinations are dangerous
A growing number of people are turning to herbal remedies and nutritional supplements not only as the sole treatment of symptoms or illness but also in combination with OTC or prescription medications. According to Dr. Hsiang-Wen Lin from the College of Pharmacy, China Medical School,, a co-author of the new study on herb and drug interactions, more than half of patients in the United States who have a chronic disease or cancer take herbs and dietary supplements, often along with their prescribed drugs.
Too often, patients do not tell their healthcare providers about the "other" substances they are taking because they are afraid their doctor will tell them to stop or they don't want the doctor to know. Yet withholding such information can have harmful, unintended consequences and seriously hamper a treatment plan and a patient's ability to improve or be cured.
In a new study published in the International Journal of Clinical Practice, reviewers evaluated 54 review articles and 31 original studies to determine the extent of problems associated with taking herbal remedies and nutritional supplements along with prescribed medication. The review included 213 herb and dietary supplements, 509 prescribed drugs, and 882 herb/dietary supplement and drug interactions.
Here are some of their findings:
- Patients with cardiovascular or central nervous system conditions who are taking medications are especially at risk for potentially dangerous herb and drug interactions
- The herbs and dietary supplement ingredients that have the greatest potential for causing negative interactions with drugs are calcium, echinacea, flaxseed, ginkgo, iron, magnesium, St. John's wort, and yohimbe
- Drugs that had the greatest number of reported interactions with herbs and dietary supplements were aspirin, digoxin, insulin, ticlopidine, and warfarin
- Types of problems associated with combining herbs or dietary supplements with medications included abdominal pain, chest pain, headache, and mild to severe heart problems
- Slightly more than 26 percent of the herb and drug interactions were major
- More than 42 percent of the drug interactions were caused by the herb or dietary supplement changing how a drug was absorbed, metabolized, and eliminated from the body
- Herbs and other botanical remedies were more likely to have reported drug interactions than were dietary supplements such as vitamins, minerals, and amino acids
Not all interactions are bad
Other research has also shown that combining herbs or dietary supplements with medications is not always bad. For example, a recent study conducted at the University of Chicago noted that "multiple constituents in botanicals may also yield beneficial pharmacological activities."
In their review, the authors looked specifically at cancer patients and pointed out that some herbal remedies, such as ginseng, have demonstrated scientific evidence that they enhance the effects of chemotherapy. In another study published in 2012, the authors reviewed how antidiabetes drugs interact with herbs in a positive way, including improving glucose control.
A 2010 study in Bioscience Trends noted that herbal medicines such as astragalus, turmeric, ginseng, and others, which are used by cancer patients, have been shown to be effective. The authors explained that "preclinical and clinical studies have shown that these Chinese herbal medicines possess great advantages in terms of suppressing tumor progression [and] increasing the sensitivity of chemo- and radio-therapeutics."
What the new study means
According to Professor Edzard Ernst, emeritus professor at the University of Exeter, who penned an editorial on the review concerning herb and drug interactions, "the potential for such interactions is substantial," and that "despite the considerable amount of documented harm generated by such interactions, our current knowledge is still woefully incomplete."
Ernst provided some advice, stating that it's the duty of doctors to provide their patients with information about potential herb and dietary supplement interactions with drugs and they should routinely ask their patients about their use of alternative medicine.
The list of herbs, dietary supplements, and drugs mentioned in this study are ones commonly taken by millions of people. It's the responsibility of patients to be honest with their doctors and to reveal any herbs and dietary supplements they are taking so physicians can determine any potential dangerous drug interactions.
Ernst E. Interactions between drugs and supplements: the tip of an iceberg? International Journal of Clinical Practice 2012 Nov; 66(11): 1019-20
Qi F et al. Chinese herbal medicines as adjuvant treatment during chemo- or radio-therapy for cancer. Bioscience Trends 2010 Dec; 4(6): 297-307
Rai A et a. Interaction of herbs and glibenclamide: a review. ISRN Pharmacology 2012; 659478
Tsai H-H et al. Evaluation of documented drug interactions and contraindications associated with herbs and dietary supplements: a systematic literature review. International Journal of Clinical Practice 2012 Nov; 66(11): 1056-78
Wang CZ et al. Herbal medicines as adjuvants for cancer therapeutics. American Journal of Chinese Medicine 2012; 40(4): 657-69