Drug-Nutrient Interactions and Drug-Supplement Interactions | Examples of Dietary Supplement Interactions

Almost half of all Americans say they have taken a dietary supplement. A dietary supplement is a vitamin, mineral, or herb that you take to improve your health or wellness. Many people believe that supplements are safe to take. But some can affect the way your body processes prescription and over-the-counter medicines. When this happens, your medicine may not work the way it should. This is called a drug-supplement interaction. It can cause serious problems.

Path to improved health

Here are some dietary supplements that could cause problems with other medicines you may be taking.

Bilberry

Possible drug-supplement interaction with:

  • Diabetes medicines. Can decrease blood sugar, which can cause blood sugar to reach dangerously low levels.
  • Anticoagulant/antiplatelet medicines (such as warfarin). Can slow blood clotting, which can increase the risk of bruising and bleeding.

Black Cohosh

Black cohosh has been used for arthritis and muscle pain. It is most commonly used to treat symptoms of menopause, such as hot flashes and night sweats, or premenstrual syndrome.

Possible drug-supplement interaction with:

  • Medicines changed by the liver. Some medicines are processed and broken down using the liver’s cytochrome P450 enzyme system. Black cohosh may decrease how quickly the liver breaks down these medicines, which can increase effects and side effects. Talk to your doctor to see if you are taking a medicine that is changed by the liver (examples are listed below).

Chaste Tree Berry

Possible drug-supplement interaction with:

  • Birth control pills. Can affect hormone levels, decreasing effectiveness.
  • Dopamine receptor antagonists. Can affect how the body breaks down the medicine.

Cranberry

Possible drug-supplement interaction with:

  • Warfarin. Cranberry may increase the amount of time warfarin is in the body. This increases the risk of bruising and bleeding.

Devil’s Claw

Possible drug-supplement interaction with:

  • Medicines changed by the liver. Some medicines are processed and broken down using the liver’s cytochrome P450 enzyme system. Devil’s claw may decrease how quickly the liver breaks down these medicines, which can increase the effects and side effects. Talk to your doctor to see if you are taking a medicine that is changed by the liver (examples are listed below).
  • Warfarin. Can decrease the effectiveness of warfarin, increasing the risk of blood clots.

Echinacea

Possible drug-supplement interaction with:

  • Caffeine. May decrease how quickly the body breaks down caffeine, causing jitteriness, headache, and rapid heartbeat.
  • Medicines changed by the liver. Some medicines are processed and broken down using the liver’s cytochrome P450 enzyme system. Echinacea may decrease how quickly the liver breaks down these medicines, which can increase effects and side effects. Talk to your doctor to see if you are taking a medicine that is changed by the liver (examples are listed below).
  • Immunosupressants. May increase activity of the immune system, which can decrease the effectiveness of the immunosuppressant.

Feverfew

Possible drug-supplement interaction with:

  • Medicines changed by the liver. Some medicines are processed and broken down using the liver’s cytochrome P450 enzyme system. Feverfew may decrease how quickly the liver breaks down these medicines, which can increase the effects and side effects. Talk to your doctor to see if you are taking a medicine that is changed by the liver (examples are listed below).
  • Anticoagulant/antiplatelet medicines (such as warfarin). Can slow blood clotting, which can increase the risk of bruising and bleeding.

Garlic

Possible drug-supplement interaction with:

  • Isoniazid. Can reduce amount of isoniazid body absorbs, decreasing effectiveness.
  • HIV/AIDS Medicines. Can increase how fast medicine is broken down, reducing effectiveness.
  • Saquinavir. Can increase how fast medicine is broken down, reducing effectiveness.
  • Anticoagulant/antiplatelet medicines (such as warfarin). Can slow blood clotting, which can increase the risk of bruising and bleeding.

Ginkgo Biloba

Possible drug-supplement interaction with:

  • Alprazolam. May decrease the effects of alprazolam.
  • Efavirenz. May decrease effectiveness of efavirenz, used to treat HIV.
  • Ibuprofen. Slows blood clotting, which increases the chance of bruising and bleeding.
  • Medicines changed by the liver. Some medicines are processed and broken down using the liver’s cytochrome P450 enzyme system. Ginkgo may decrease how quickly the liver breaks down these medicines, which can increase effects and side effects. Talk to your doctor to see if you are taking a medicine that is changed by the liver (examples are listed below).
  • Diabetes medicines. May affect insulin levels, which can decrease effectiveness of the medicines.
  • Anticonvulsants. May affect chemicals in the brain, which can decrease effectiveness of the anticonvulsants.
  • Trazodone. May affect chemicals in the brain, which can cause serious side effects in the brain.
  • Warfarin. May slow blood clotting in addition to the warfarin, which can increase chance of bruising and bleeding.

Ginseng

Possible drug-supplement interaction with:

  • Warfarin. May decrease the effectiveness of warfarin, which can increase the risk of blood clots.

Goldenseal

Possible drug-supplement interaction with:

  • Cyclosporine. Can decrease how fast the body breaks down cyclosporine, which can increase side effects.
  • Medicines changed by the liver. Some medicines are processed and broken down using the liver’s cytochrome P450 enzyme system. Goldenseal may decrease how quickly the liver breaks down these medicines, which can increase the effects and side effects. Talk to your doctor to see if you are taking a medicine that is changed by the liver (examples are listed below).
  • Medicines moved by pumps in cells (P-Glycoprotein Substrates). Can make pumps less active, increasing amount of medicine absorbed by the body.

Studies suggest that the risk of interaction with this supplement is high. Talk to your doctor before you take goldenseal.

Horse Chestnut

Possible drug-supplement interaction with:

  • Lithium. Can decrease how well body gets rid of lithium, which can cause serious side effects.
  • Diabetes medicines. Can decrease blood sugar, causing blood sugar to reach dangerously low levels.
  • Anticoagulant/antiplatelet medicines (such as warfarin). Can slow blood clotting, which can increase the risk of bruising and bleeding.

Kava

Possible drug-supplement interaction with:

  • Alprazolam and CNS depressants. Can cause too much drowsiness and sleepiness.
  • Medicines changed by the liver. Some medicines are processed and broken down using the liver’s cytochrome P450 enzyme system. Kava may decrease how quickly the liver breaks down these medicines, which can increase the effects and side effects. Talk to your doctor to see if you are taking a medicine that is changed by the liver (examples are listed below).

Licorice

Possible drug-supplement interaction with:

  • Diuretics, corticosteriods. Can reduce potassium to dangerously low levels.
  • Can affect levels of cortisol in the body, affecting the medicine’s ability to work properly.
  • Medicines changed by the liver. Some medicines are processed and broken down using the liver’s cytochrome P450 enzyme system. Licorice may decrease how quickly the liver breaks down these medicines, which can increase the effects and side effects. Talk to your doctor to see if you are taking a medicine that is changed by the liver (examples are listed below).
  • Anticoagulant/antiplatelet medicines (such as warfarin). Can slow blood clotting, which can increase the risk of bruising and bleeding.

Milk Thistle

Possible drug-supplement interaction with:

  • Medicines changed by the liver. Some medicines are processed and broken down using the liver’s cytochrome P450 enzyme system. Milk thistle may decrease how quickly the liver breaks down these medicines, which can increase the effects and side effects. Talk to your doctor to see if you are taking a medicine that is changed by the liver (examples are listed below).
  • Glucuronidated medicines. Can decrease how well liver breaks down the medicines, which can increase or decrease its effectiveness.
  • Tamoxifen. Can increase how much tamoxifen is absorbed by the body.

Saw Palmetto

Possible drug-supplement interaction with:

  • Birth control pills. Can decrease effects of estrogen in the body, which can reduce the effectiveness of birth control pills.
  • Estrogen. Can decrease estrogen levels in the body, which can decrease the effectiveness of estrogen pills.
  • Warfarin. Can slow blood clotting, which can increase the risk of bruising and bleeding.

St. John’s Wort

St. John’s Wort has many possible drug-supplement interactions, including but not limited to:

  • Cyclosporine. Can increase how quickly the body breaks cyclosporine down.
  • Digoxin. Can decrease the amount of digoxin the body absorbs, decreasing the effects of digoxin.
  • Some antidepressants. Can increase serotonin levels too much, causing serious side effects including heart problems, shivering, nausea, headache, and anxiety.
  • Birth control pills. Can increase the breakdown of estrogen, decreasing the effectiveness of birth control.
  • Warfarin. Can increase the breakdown and decrease the effectiveness of warfarin, possibly increasing the risk of clotting.

Talk to your doctor before you take St. John’s Wort.

Soy isoflavones

Possible drug-supplement interaction with:

  • Estrogen. Soy isoflavones may decrease the effectiveness of estrogen pills.
  • Tamoxifen. Can affect estrogen levels, decreasing effectiveness of tamoxifen.
  • Warfarin. Can decrease the effectiveness of warfarin, increasing the risk of bruising and bleeding.

Turmeric (curcurmin)

Possible drug-supplement interaction with:

  • Anticoagulant/Antiplatelet drugs (such as warfarin). Can slow blood clotting, which can increase the risk of bruising and bleeding.

Valerian

Possible drug-supplement interaction with:

  • Alcohol. Can cause drowsiness in addition to the alcohol, resulting in too much sleepiness.
  • Sedative medicines (benzodiazepines and CNS depressants). Can cause drowsiness in addition to the effect of the sedative, resulting in too much sleepiness.

Examples of medicines changed by the liver can include: amitriptyline, diazepam, zileuton, celecoxib, diclofenac, fluvastatin, glipizide, ibuprofen, irbesartan, losartan, phenytoin, piroxicam, tamoxifen, tolbutamide, torsemide, warfarin, lovastatin, ketoconazole, itraconazole, fexofenadine, triazolam, and many others.

Things to consider

Don’t take any herbal health products or supplements without talking to your family doctor first. This is especially the case if you take any other prescription or over-the-counter medicine. If you do use an herbal health product or supplement, read the directions on the label to learn how much to take and how often to take it. You should never take more than the recommended amount. If you have any questions about how much to take, ask your doctor.

The National Center for Complementary and Alternative Medicine (NCCAM) and the Office of Dietary Supplements are good sources of information about herbal health products and supplements.

Questions to ask your doctor

  • Is it safe for me to take _________ supplement?
  • What interactions might the supplement cause with medicines I am taking?
  • Is there a different medicine I can take that won’t cause interactions?
  • There are so many supplements available at the store. How do I pick the right one for me?