Traditional Research | Herbal Usage Guidance


Throughout our history we have relied on plants for both food and medicine; thus our bodies have evolved an ability to assimilate the bio-active compounds in plants. This evolutionary relationship is important to herbal medicine because the body is accustomed to assimilating the more potent chemicals of herbs within the matrix of the whole plant. Thus, properly used, herbs can often work with a high degree of effectiveness without the side-effects common in prescription drugs or over-the-counter medications.

Herbal Formulas

While many cultures have used herbs as simples (one herb at a time) the history of herbal medicine and the great systems of medicine reflects a focus on polypharmacy. This means most herbs are given in complex formulas that create a unique synergy. A well constructed formula can increase activity, decrease toxicity, avoid herb-drug interactions and improve patient outcomes. This concept of synergy-using a whole plant extract rather than an isolated constituent and a well chosen formula rather than a single herb for a single disease-is one of the foundational elements of good herbal medicine.

Herbs—Safe Use

There are a few simple guidelines for safe use of these formulas and herbs in general:

  1. When using an herb or formula for the first time, it is wise to take only 1/4 the recommended dosage to make sure you will not have an adverse reaction to it. If such a reaction occurs, immediately discontinue using the herb or herbal product. Slowly increase the dosage over 2 weeks until you are at the recommended dose level.
  2. Always pay careful attention to recommended use or dosage. “If a little is good more must be better” does not apply here. Many herbs, particularly the stronger medicines used to treat chronic problems, are best used in small doses taken over an extended period of time.
  3. There are few herbs that are truly safe during pregnancy. If you have a history of miscarriage or problem pregnancy consult a midwife or competent physician before trying herbs.
  4. Know yourself! Always use common sense and careful discretion when choosing appropriate remedies for yourself. If you try something and it doesn’t work for you, you may have misinterpreted your symptoms and should consult a health care practitioner. But be patient, the actions of many herbs are subtle and only manifest when used over time.
  5. If you are taking prescription drugs, interactions between some herbs and pharmaceuticals are possible. Discussing these possibilities with a clinical herbalist, professional member of the American Herbalists Guild, knowledgeable pharmacist or physician is advised.

Herbs Contraindications

Classification System —Many traditions of herbal medicine have systems for classifying plants by their relative safety. For example, in Native American Cherokee theory Foods are herbs that can be used as tonics every day with no potential for problems. Medicines are herbs that are used for a specific purpose for a specific duration because they are more powerful in their activity. Poisons are herbs only used in tiny doses under the supervision of experienced and competent practitioners. Traditional Chinese Medicine uses the terms Superior for food or very safe herbs and Inferior for those with more potential for toxicity or side effects.

Energetics It is important to keep in mind the energetic properties of herbs in relationship to the condition being treated. For example, when treating a hot condition—red, inflamed, hot to the touch—a cool, soothing herb like marshmallow will be most helpful. Using a hot herb like Ginger could irritate the tissue even more.

Pregnancy During pregnancy and nursing one must consider the dose of any medicine that the baby may receive through the placenta or milk. Any very bitter tonic or laxative can cause contractions of the uterus as a reaction from stimulating other organs. For simple home remedies a pregnant or nursing mother would be wise to limit her choices to food or superior herbs taken in teas. Teas are assimilated more slowly than extracts and would therefore have a milder impact on the baby.


With the increase in those taking both herbs and drugs, the potential for herb-drug interactions exist, but we need to put the issue into perspective. Food/drug interactions are far more common, as we consume far greater quantities of food than herbal medicines. Grapefruit juice inhibits liver detoxification activity and can increase serum levels of many drugs including calcium antagonists and anthistamines. Milk interferes with absorption of Tetracycline by 50-90%. Green leafy vegetables (spinach, cabbage, beet greens, kale), broccoli, peas and cucumbers, can alter coagulation and interact with anticoagulant medications. Drug/drug interactions are even more common. Even the seemingly benign antacids with polyvalent minerals (Ca, Fe, Mg, Zn, Al) can interfere with cycline and mycin antibiotics. Tobacco smoke is of the most potent substances affecting liver detoxification activity—it decreases blood levels of many medications and vitamin C. In fact, the potential for drug/drug interaction for those patients taking multiple drugs (6 or more) is close to 100%.

Herb-Drug Interactions

Herb/drug interactions occur, but note the types of herb/drug interactions and that many are actually positive and could result in the ability to decrease drug dosage:

  1. Decreased bioavailability of medicine - decreased absorption (Psyllium Seed, Flax Seed, Slippery Elm), enhanced metabolism (Brassicas), or enhanced elimination (Senna, Coffee, Cascara Sagrada).
  2. Increased bioavailability of medicine - increased absorption (Ginger, Cayenne, Prickly Ash, Black Pepper), decreased metabolism (Grapefruit juice), or decreased elimination (Licorice).
  3. Potentiation of drug’s effects - via a different but complementary action (Siberian Ginseng & antibiotics).
  4. Potentiation of drug’s effects via similar activity (Lasix & Dandelion Leaf, Digoxin & Lily of the Valley).
  5. Protection from adverse drug effects (Milk Thistle & hepatotoxic / nephrotoxic herbs, Licorice & corticosteroids).
  6. 6. Antagonistic or incompatible activities (laxatives & astringents, CNS stimulants & sedatives).

Simple Guidelines—When evaluating a potential interaction

  1. Be specific about:
    a. herb product dose, form (tea, extract, capsule), brand, other ingredients
    b. any medications taken
    c. foods consumed
  2. Record timing of occurence-plausible pharmacological timing is more likely to be within a few hours or a day or two rather than weeks or months later.
  3. Does reaction occur on re-challenge? (Do not attempt this without clinical supervision.)
  4. Does reaction cease on stopping herb?

Predicting/Preventing Interactions—A Few Simple Rules

  1. Follow traditional knowledge of herb activity to predict and prevent possible synergies or antagonisms with prescription drugs.
    • Hawthorn may potentiate Digitaloids (Digoxin, Lanoxin and Beta-blockers).
    • Diuretics such as Buchu, Uva-Ursi, Juniper, etc. are contra-indicated while taking Lithium.
    • Herbs with Vitamin K such as Shepherd’s Purse & Nettles should not be added to the diet in large amounts if taking blood thinners.
    • Garlic, Ginkgo and Horse Chestnut should be used cautiously taken with prescription blood thinners (Dicoumarin).
    • MAO inhibitors such as Licorice and Passionflower should not be used with benzodiazepine medications.
    • Valerian, Hops and Kava may potentiate the effects of benzodiazepines, barbituates or moderate alcohol consumption.
    • Mucilagenous herbs like Slippery Elm and Marshmallow may reduce absorption of other medications.
    • Laxative and diuretic herbs may increase potassium loss, therefore increasing the toxicity of cardiac glycosides present in Digoxin, Digitoxin or Lanoxin.
    • Cola nut is contra-indicated with MAO inhibitors and with ephedrine containing drugs.
  2. Use formulas and lower dosages of herbs with potential problems - a recent study of St. John’s wort showed that its ability to provoke a herb/drug interaction was dose dependent. In traditional herbal medicine herbs are usually used in formulas, thus reducing the amount of any one herb ingested.
  3. Take herbs & drugs separately (by 2-3 hours).
  4. When adding herbs to already established drug regimens, start at low dose and gradually increase the dose. Monitor patients carefully.
  5. Avoid starting or stopping medications and herbs suddenly. Subtle changes may not create a problem but substantial changes may trigger a major response.
  6. Avoid red flags - Warfarin - interacts with over 200 foods, drugs, etc. Other problematic drugs include protease inhibitors, Cyclosporin, & Digoxin. Use care combining herbs, drugs, or supplements with medications that have a narrow therapeutic index.
  7. Avoid using Kava with hepatotoxic medications (tetracycline, statin drugs, excessive alcohol, acetominophin).
  8. Studies indicate St. John’s wort has the ability to stimulate Phase I liver detoxification (cyclic P-450 activity-CYP3A4, CYP2D6 and CYP2E1) and P-Glycoprotein activity in the gut. Medications known to be metabolised via these pathways may have reduced blood levels if taken with St. John’s wort. Avoid using St. John’s wort with protease inhibitors, Cyclosporin, Irinotecan, Digoxin and Warfarin.

Herbal Therapeutics Research Library, David Winston (RH) AHG

©2012 Herbal Therapeutics Research Library. All rights reserved

*Disclaimer: The information on historical, ethnobotanical and phytotherapeutic uses of herbs and traditional formulas contained herein is based on the experience and research of the author. It is not intended as a substitute for consulting with your physician or other health care provider. Any attempt to diagnose and treat an illness should be done under the direction of a health care professional. The publisher and author are not responsible for any adverse effects or consequences resulting from the use of any of the information discussed. Should you have any questions concerning the appropriateness of any preparation mentioned, the author strongly suggests consulting a professional health care advisor.