Drug Interactions - Drug interactions with herbs & healthfoods

Drug interactions with herbs & healthfoods

Vitamin & Mineral

Nutritional Benefit and Function

Relationships & Interactions

Vitamin A

Essential for the health of the skin
Necessary for the proper functioning of the immune system. Important for good vision. Needed for maintenance & growth of teeth, nails bones, and hair
In Beta-Carotene form: Antioxidant, free radical fighter

Works synergistically with Vitamins C and E
Occurs with Vitamin D in fish oils

Vitamin C

Contributes to the health of teeth and gums. Necessary for the proper functioning of the immune system Required for production of collagen
Antioxidant, free radical fighter

Enhances the absorption if Iron Enhances effectiveness of B-12, Folic, Acid, B-6 Works with Vitamin E

Vitamin D

Necessary for the formation of strong teeth and bones

Occurs naturally with Vitamin A in fish oils. Regulates metabolism of Calcium & phosphorus

Vitamin E

Antioxidant, free radical fighter
Necessary for the proper functioning of the immune system. prolongs life of red blood cells. Involved in metabolism of polyunsaturated fatty acids

Works synergistically with Selenium and Vitamin A. Inorganic Iron can destroy Vitamin E when taken together

Thiamine (B-1)

Necessary for carbohydrate metabolism
Necessary for good muscle coordinates
maintains normal appetite, digestion & nerve activity. Involved in normal energy production

Interacts with other B-Vitaminns

Riboflavin (B-2)

Helps maintain health skin and eyes
Involved in converting fats, proteins and carbohydrates into energy

Interacts with other B- Vitamins


Involved in metabolism of fats, carbohydrates and protein. Involved in normal stomach fluid & bile secretions

Interacts with other B- Vitamins

Vitamin (B-6)

Involved in carbohydrate, fat & protein metabolism. Needed for production of antibodies and red blood cells

Interacts with other B-Vitamin & Vitamin C Involved in metabolism of polyunsaturated fatty acids

Folic Acids

Helps maintain healthy blood
Involved in the formation of red blood cells. Essential for synthesis of generic material and the metabolism and amino acids

Interacts with other B- Vitamins & Vitamin C

panthothenic Acids

Involved in formation of hormones and vital compounds which regulate nervous system. Essential for the release of energy from carbohydrates

Interacts with other B-Vitamins


Involved in the normal metabolism carbohydrates, fats & proteins. Needed for maintenance of skin cells, nervous system & intestines

Works with Vitamin B-2, B-6, A & D for skin maintenance

Cobalamin (B-12)

Required for the development of normal red blood cells. Necessary for normal function of skin cells, nervous system & intestines

Interacts with other B-Vitamins
Enhances utilization of Vitamin A & Beta Carotene


Most abundant minerals in the human body. Essential for the strong bones and teeth. Essential for muscle contraction & heartbeat. plays an important nutritional role in preventing osteoporosis (fragile bones)

Vitamin D aids in calcium absorption


Is found in bones and teeth
Helps to maintain muscle contractions
Activates enzymatic reactions related to metabolism and energy productions

Vitamin D


Aids Calcium in forming bones and teeth
Needed for metabolic processes of all cells



Essential for transport of oxygen through the blood

Some inorganic Iron can destroy Vitamin E. Vitamin C enhances Iron uptake


Necessary for the proper functioning of the immune system. Involved in many enzymatic reactions including carbohydrate metabolism and the synthesis of protein and genetic material
Involved in normal function of the prostate

Balances with Copper


Works with Sodium to maintain proper muscle function. plays a role in the normal activity of the heart, muscle and nervous system

Balances with Sodium


Involved in production of thyroid hormones. Necessary for proper growth

Not to be taken if on medication for Thyroid


Involved in the conversion of blood sugar into energy


Involved in metabolism of fats and proteins. Involved in energy production
Necessary for the synthesis of cartilage


A component of the antioxidant enzyme glutathione peroxides. Necessary for the proper functioning of the immune system. Antioxidant, free radical fighter

Herb and Drug Interactions

Following is information not verified or researched by me. The apparent author source is listed below. This information suggests certain circumstances in which using herbs may cause concerns. Since this information was not confirmed please use it in an advisory manner. To me this information suggests caution if considering using herbs.

  • Echinacea,if used for more than eight consecutive weeks, could cause liver toxicity and should not be used with drugs such as anabolic steroids, amiodarone and methotrexate which are toxic to the liver as the affect may be additive.
  • Feverfew, garlic, ginger, ginseng, and ginkgo biloba all affect bleeding time and should not be taken by patients using warfarin or by patients that have decreased platelet counts.
  • St John's wort should not be taken with monoamine oxidase inhibitors or selective serotonin reuptake inhibitors like prozac and paxil until more information is available. people on heart treatment, HIV treatment, Taking the birth control pill, should consult there Gp before taking St John's Wort, or if already taking St John's Wort not stop taking it before consulting there Gp
  • Licorice, plantain, hawthorn and ginseng may interfere with digoxin therapy and valerian root should not be taken when barbiturates are used because it could cause an increase in the barbituate effects.
  • 'Evening primrose oil and borage are contraindicated in patients taking anticonvulsants (eg clonazepam).
  • lmmunostimulants such as echinacea and zinc should not be given with immuno suppressants such as corticosteroids (like prednisone) and cyclosporine and are contraindicated in patients suffering from rheumatoid arthritis, systemic lupus erythematosus and autoimmune hepatiitis.
  • Source: Hans Larsen is a health sciences researcher living in Victoria, British Columbia from Alive Magazine March 1999 with some changes by D. Morrow

Feverfew: taken to reduce the severity of migraines. Do not take with other migraine medications, as, it may raise heart rate and blood pressure. Feverfew has the potential to react with anti-coagulants, increasing the thinning of blood.

Ginkgo: increases blood flow and circulation throughout the body, can also help improve memory. May interact with anti-coagulant medications such as Aspirin, Coumadin, heparin and warfarin, causing the blood to thin too much, and provoking a serious bleeding disorder. A recent report in the New England Journal of Medicine describes a case of a man who'd been taking Aspirin to prevent a heart attack and had spontaneous bleeding into the eye from the iris within a week of taking a daily dose of ginkgo.

Garlic: is thought to help lower cholesterol and prevent the formation of blood clots that could lead to heart attacks. Garlic capsules may increase blood thinning if you are already on anti-coagulants. Do not take with diabetes medication because it may cause a decrease in blood sugars.

Ginseng: used to help reduce stress, boost energy and improve stamina, and may also help lower cholesterol. Can cause nervousness and excitation, and overuse can lead to headaches, insomnia and heart palpitations. Can increase blood pressure. Should not be used if you are taking prescriptions for high blood pressure or Coumadin.

Hawthorn: claimed to be effective in helping reduce angina attacks by lowering blood pressure and cholesterol levels. Should not be taken digoxin, a heart medication. The mix may lower heart rate too much.

Licorice: used to treat coughs, colds and peptic ulcers. High doses can lead to increased blood pressure, water retention and potassium loss. Do not use with diuretics or digoxin because it could lead to further loss of potassium, essential for heart function.

St. John's wort: a natural anti-depressant for mild to moderate depression. Do not take with other anti-depressant medications.

Valerian: a mild sedative with hypnotic effects, used to promote sleep, Should not be taken with alcohol or Valium.

Feverfew, featherfew, bachelors button, featherfoil, febrifuge plant, midsummer daisy

Uses: This herb has been used as an anti-inflammatory. It can also help the pain associated with migraine headaches. Feverfew can also help to soothe menstrual cramps. It may help as a digestive aid.

Route: This herb should be taken by mouth only.

precautions: If you are pregnant, do not take this herb due to its folk history as a menstruation promoter. Feverfew can cause mouth sores and sometimes abdominal pains. If you are taking blood thinners, do not take this herb.

Do not give feverfew to children under the age of two. Feverfew should be used in medicinal amounts only in consultation with your healthcare provider.

Availability: for migraines or as an anti-inflammatory 100-200mg a day

May also use 1/2 to 1 teaspoon per cup of boiling water. Steep for 5-10 minutes, drink up to 2 cups a day

Chew two fresh or frozen leaves a day

Turmeric, curcuma, Indian saffron

Uses: This herb has been used as an anti-inflammatory. It can decrease inflammation caused by arthritis. It works like ibuprofen but does not decrease the pain as effectively. It will decrease the inflammation. This herb has also been use to decrease intestinal gas, and as a poultice for pain or ringworm.

Route: please take this herb by mouth only. It is available in tablet form and also as a spice. If taken in tablet form, please take once a day.

precautions: If you are taking any blood thinners, do not take this herb without first discussing it with your physician, pharmacist, or nurse. Report any bleeding gums nosebleeds, or increased bruising to your healthcare provider. please anytime you take any additional therapies check with your healthcare provider first. If you are taking chemotherapy, do not take this herb. If you are pregnant, please discuss this with your physician before taking this herb or any herb. Do not give to children under the age of two.

Availability: 400-1200 mg daily

For an infusion, use 1 teaspoon of turmeric powder per cup of warm milk. Drink up to 3 cups a day.

Ginger, Jamaica ginger, African ginger or Cochin ginger

Uses: This herb has been used as an anti-inflammatory, for motion sickness, for nausea and vomiting.

Route: please take this by mouth only.

precautions: Do not take this herb if you are pregnant, have a history of congestive heart failure, or are taking blood thinners. If taken with other anti-inflammatories that cause stomach upset, ginger could make this worse. Do not take if you have a history of an ulcer or renal failure. Ginger is on the Food and Drug Administration's list of herbs generally regarded as safe. For healthy adults, ginger is safe in amounts typically recommended. Ginger should be used in medicinal amounts only in consultation with a healthcare provider.

Side effects: heartburn

Availability: 1500mg daily for as an anti-inflammatory

1500mg 30-60 minutes before travel for motion sickness

Ginger tea- 2 teaspoons of powdered or grated root per cup of boiling water, steep for 10 minutes

If You Are pregnant Or Lactating Do Not Take Any Herbal products Without Consulting Your HealthCare provider.


  • Biopharmaceutic
  • Therapeutic
  • Anecdotal


  1. Tannin containing herbs may cut down on iron absorption due to poorly absorbed iron tannate complexes.
    Dister, et. al. Gut 16:193-200, 1975.
  2. Tannin containing beverages may reduce B12 absorption due to formation of glycoprotein-B12-tannic acid complexes.
    Carrera, et. al. CR Acad Sci 2 (6):239-242, 1973.
  3. Ca, Mg, Fe containing herbs may bind or inactivate tetracycline analogues.
    Food Drug Interactions 2:1-18 ER Squibb, 1978.
  4. Vitamin C may affect the excretion of weakly basic herbs that undergo tubular reabsorption in alkaline urine.
    Food Drug Interactions 2:1-18 ER Squibb, 1978.
  5. Herbs that exhibit hepatotoxicity may inhibit certain liver microsomal hydroxylating systems.
    Morbidity Mortality Week Report 27:248-249, 1978. Segeiman, et. al. JAMA 236:477, 1976.
  6. Herbs that exhibit renal toxicity may alter the excretory mechanism of concurrently administered drugs.
    Segelman, et. al. JAMA 238:47, 1976.
  7. Bearberry Uva-Ursi is inactivated by urinary acidifiers (i..e. cranberry juice)
    Review of Natural products 1996, Facts and Comparisons
  8. Sarsaparilla may interfere with absorption of simultaneously administered drugs. Increases absorption of digitalis and bismuth, and elimination of hypnotics.
    Osborne F, Chandler F 1996; Canadian pharmaceutical Journal


  1. potassium chloride sold in health food stores may cause toxicities due to alteration of electrolyte balance.
    Stephenson Consumer p. 19-21, Sept 1978.
  2. Herbs with hypoglycemic action may affect the amount of antidiabetic drug required.
    Farnsworth Title and Till 57:52-56, 1971.
  3. L-Tryptophan and magnesium salts may interfere with antidepressant or anxiolytic therapy.
  4. Aloe may potentiate toxicity of cardiac glycosides and thiazide diuretics.
    Remington Apr 1997; Calif pharm (suppl):1-10
  5. St. John's Wort has three-fold antidepressant mechanisms (reuptake inhibitor, MAOI, COMT inhibitor). Should avoid tyramine- containing foods and serotonergic agents. Avoid combinations with photosensitivity producing agents.
    Inpharma 1996; No. 1058:3-4, Oct 12
  6. Licorice root (glycerhizza) may interfere with antihypertensive thiazide diuretics therapy.
    Koster, Medical Intelligence 278:1381, 1968 Chamberlain, JAMA 213:1343, 1970
  7. Bran products, wheat germ, yeast prepartions may interfere with levodopa therapy.
    Food and Drug Interactions 2:1-18 E.R. Squibb, 1978.
  8. Yeast preparations can interfere with antihypertensive therapy.
    Food and Drug Interactions 2:1-18 E.R. Squibb, 1978.
  9. Ginkgo biloba extracts in combination with aspirin and other anticoagulants may cause subdural hematomas
    One case of retinal hemorrhage associated with Ginkgo biloba and aspirin.
    Neurology 1996; 46: 1775-1776
  10. Valerian not synergistic with alcohol, but has not been studied with opiates or other CNS depressants.
    Tyler 1996; JAphA NS3(1):29-37
  11. Ginkgo or feverfew may cause platelet aggregation in combination with coumadin.
    Tyler 1994; Herbs of Choice, Haworth press
  12. Feverfew should not be used concomitantly with estrogens & progestagens progesterone.
    Herbal prescriptions for Better Health, 1996, p 15.
  13. Ginseng may cause a hypoglycemic effect in diabetics.
    Case report of ginseng and furosemide decreased diuretic effect resulted in hospitalization probably germanium contamination.
    Becker et al. 1996; JAMA 276:606-607
  14. Saw palmetto should not be used in combination with agents for benign prostatic hypertrophy.
    Effect on other hormone therapy unknown.
    Herbal prescriptions for Better Health, 1996, p 15.
  15. Statins inhibit HMG-CoA reductase
    (req for chol & CoQ10 synthesis)
    Beta blockers propranolol & metaprolol, phenothiazines & TCAs inhibit CoQ10 dependent enzymes.
    Alernative Medicine Review 1998; 3(1): 58-59
  16. Feverfew should not be used concomitantly with estrogens & progestagens progesterone.
    Herbal prescriptions for Better Health, 1996, p 15.

Anecdotal Interactions

  1. Juniper can increase lithium levels.
  2. Drug Interactions

    If you are taking the antihistamine Terfenadine (Seldane) you should avoid eating grapefruit or drinking grapefruit juice. Grapefruit and some other citrus fruits contain chemicals that inhibit enzymes involved in the metabolism of this drug.

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