By Michelle Simon, PhD, ND

Don’t underestimate the power of the herbal supplements you take. While herbs are in general gentler than drugs, when you mix the two together you run the risk of powerful interactions. If you’re taking any prescription medicines, be sure to consult with your doctor or pharmacist before taking a supplement. We’ve rounded up five of the most relevant herb-drug interactions for you to keep an eye on.

  1. Ginseng
    One of the most popular herbs in the United States, immune-boosting ginseng is a powerful adaptogen and can boost stamina. But its effectiveness can become a liability when combined with certain drugs. Ginseng can decrease the effectiveness of blood thinners such as warfarin. And because ginseng can also reduce platelet activity (clotting), combining it with aspirin or any other nonsteroidal anti-inflammatory drug NSAID isn’t recommended. In addition, according to the University of Maryland, Asian ginseng may intensify the effects of antipsychotic medications, so avoid taking them together.According to the University of Maryland’s Complementary and Alternative Medicine Guide, “There have been reports of a possible interaction between Asian ginseng and the antidepressant medication, phenelzine (which belongs to a class known as monoamine oxidase inhibitors), resulting in symptoms ranging from manic-like episodes to headache and tremulousness.”[1]


  1. Licorice
    Licorice, or “sweet root,” has a long legacy of medicinal use in both Eastern and Western medicine systems. Licorice root’s active compound, glycyrrhizin, is 50 times sweeter than table sugar. Licorice root has been used to support digestive and respiratory health. It acts as a demulcent, a soothing, coating agent good for the digestive tract, and as an expectorant, a substance that loosens up phlegm. There are several drugs that should not be combined with licorice. If you take angiotensin-converting enzyme (ACE) inhibitors or diuretics to regulate blood pressure and also use licorice products, you could lose too much potassium. Diuretics cause a loss of potassium and sodium, while the glycyrrhizin in licorice encourages the body to conserve sodium and lose potassium. If combined, it can add up to elevated blood pressure.Licorice should also not be taken with digoxin, as it can amplify the drug’s toxic effects; insulin or diabetes medication, as licorice can affect blood sugar levels; or blood thinners, as it can dilute their effect.[2]


  1. Peppermint
    An herb that eases digestion, peppermint loses its efficacy if it’s consumed at the same time as an antacid. That’s because drugs that reduce stomach acid can dissolve the peppermint capsules’ coating in the stomach instead of the intestines, reducing peppermint’s beneficial impact. To work around this, take peppermint either two hours before or after you take your antacid.


  1. Garlic
    Although garlic can help manage high blood pressure and high cholesterol, garlic or garlic pills taken in large doses also acts as blood thinner. Warfarin, other blood thinners, or regular doses of aspirin should not be combined with the use of garlic as a supplement or in large quantities.Researchers have also found that garlic supplements taken with the anti-HIV drug saquinavir, a protease inhibitor, can cause the medication levels in the blood to be more volatile and interfere with treatment.[3],[4]


  1. Valerian
    Valerian root is commonly used to help with sleep disorders and anxiety. One possible side effect of the herb is that it slows the way the liver breaks down certain drugs. If that process is inhibited, it creates a backlog of drugs in the body. Antihistamines, statins (drugs taken to lower cholesterol), and some antifungal drugs rely on the same liver enzymes that break down valerian, and so they may be less efficacious if taken together. Valerian can also make drugs used as sedatives overly effective, meaning you can get more sedation than you want—or is safe. According to the University of Maryland, beware of combining valerian with “anticonvulsants such as phenytoin (Dilantin) and valproic acid (Depakote), barbiturates, benzodiazepines such as alprazolam (Xanax) and diazepam (Valium), drugs to treat insomnia, such as zolpidem (Ambien), zaleplon (Sonata), eszopiclone (Lunesta), and ramelteon (Rozerem), certain antidepressants, and alcohol.”[5]

MichellSimonIn her practice, Dr. Simon puts a strong focus on women’s health, preventative medicine and musculoskeletal health. She is also part of several organizations, including president of the Institute for Natural Medicine, director for the American Association of Naturopathic Physicians, director of Naturopathic Physicians Research Institute, member of the Washington State Health Technology Assessment Clinical Committee and co-director of the Communities in Need/Integrated Care Options Project of the Washington Association of Naturopathic Physicians.









*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.