Drug-Herb-Vitamin Interactions

Health consultants function as educators and therefore should never prescribe any substance, food, herb, or an over-the-counter medication. Author Francis Brinker recognizes that medicinal herbs should be treated respectfully as they have significant pharmacological activity. His book, Herb Contraindications and Drug Interactions, is directed at both the qualified practitioner and the general population. Majority of herbs in traditional formulas pose no risk to the public, as they are considered mild.

However, their activity could intensify the side effects or toxic reactions to prescription medications. Brinker identifies the herbs that require caution; herb/drug interactions; herbal contraindications for mothers and children; and vitamin/mineral interactions. Herb Contraindications and Drug Interactions approaches interactions from the pharmaceutical side. Using a drug as the starting point, the authors identify which herbs and foods may cause interactions. Below are 5 points based on content from Herb Contraindications and Drug Interactions.

 1. Discuss the concerns regarding the increasing popularity and use of herbs.

Physicians, pharmacists and patients need to know that certain herbs when used in combination with pharmaceutical drugs produce contraindications that might have adverse effects on the body. This must be acknowledged and when a patient encounters himself with a serious medical problem, a qualified practitioner should be consulted, not a self medication which might not take into consideration contraindications or drug interaction knowledge.

2. Discuss the concerns regarding the increasing popularity and use of herbs.

Ginseng’s drug interaction are:

  • Insulin dosage may need adjusting due to hypoglycaemic effects in diabetic patients.
  • Anticoagulant activity of warfarin may be reduced.
  • Prelonged (13 weeks) consumption of caffeine may cause hypertension.
  • If used with monoamine oxidase inhibitor phenelzine may result in manic-like symptoms.

3. Discuss the contraindications associated with guarana.

Guarana’s contraindications are:

  • Avoid caffeine during pregnancy as increases in caffeine aare present in mother’s milk, has been associated with fetal loss, low birth weight and premature deliveries in humans, and birth defects in animals
  • Prolonged use may cause insomnia, restlessness, anxiety, irritability, stomach pains and similar effects (all speculative).
  • Psychological disorders (speculative) can aggravate depression or anxiety neurosis.
  • Heart disorders (speculative) as caffeine increases heart beat or causes exacerbating arrhythmias (empirical).
  • Duodenal ulcers (speculative) after increases in gastric acid secretion due to caffeine.
  • Kidney disorders (speculative) due to the diuretic effect of caffeine.

4. Discuss the contraindications of tobacco.

Tobacco’s contraindications are:

  • Risk of prematurity, miscarriage and neurological impairment to the baby due to lowered birth weight during pregnancy, possible damage to alveolar septa in the lungs of newborns.
  • Heart disease due to increased levels of high-density lipoprotein.
  • Increased risk of cancer in the lungs, mouth, pharyngeal, laryngeal, bladder and pancrease.
  • Increase in smoke related diseases such as ulcers, high blood pressure, osteoporosis, blood clots in legs, diabetes, heart disease, emphysema and bronchitis.
  • Exposure to toxins such as monoxide, asbestos, particulate matter, heavy metals and other xenobiotics.
  • Poor health due to lifestyle choices such as obesity, alcoholism and lack of exercise.
  • Heart disease for type A personality.
  • Surgery complications due to high levels of carbon monoxide.
  • Diminished production of breast milk during pregnancy due to nicotine, exposure to second hand smoke which causes changes in respiration, oxygen saturation in the infant, lower respiratory infections, and may change the intelligence and behavioural development and increase the chance of lung cancer.
  • Increased risk of developing cardiovascular and respiratory system conditionings and becoming an addict, high levels of acute toxicity.

5. Discuss how herb/drug interactions can modify intestinal absorption of medicines.

The use of laxatives or caffeine will decrease bowel transit time and reduce the absorption of orally administred drugs. Plants with high levels of tannins (eg Altrope belladonna, lobelia inflata), iodine, salicylates can precipitate alkaloids and interfere with some absorption of drugs (eg ephadrine, colchicine).


In the book A-Z Guide to Drug-Herb-Vitamin Interactions,  editor Alan R. Gaby, M.D., investigates the most common prescription medications and their interactions with supplements. It is based on more than 4,500 known major interactions among herbs, vitamins, foods, and drugs. Below are some points covered in the book A-Z Guide to Drug-Herb-Vitamin Interactions, by Alan R. Gaby, editor.

1. Name the two dietary supplements that may be helpful if taking antibiotics and explain why they are beneficial.

The two dietary supplements that aid antibiotics are Probiotics and Vitamin K. Probiotics are beneficial because the probiotic organism such as lactobacillus casei, lactobacillus acidophilus, bifodobacterium longum and saccharomyces boulardii help prevent one of the side effects of taking antibiotics which is diarrhea. Probiotics have also been helpful in treatment of other antibiotic side effects such as clastridium infection, overgrowth of yeast in the vagina and intestines. Vitamin K is helpful in preventing the antibiotic induced bleeding effect.

2. List the five dietary supplements that may be beneficial if taking aspirin and explain why they may be needed.

The five dietary suppments beneficial when taking aspirin are:

  1. Folic Acid – reduces the impact of the lowered levels of folic acid in people who have rheumatoid arthritis and take aspirin.
  2. Iron – counteracts the gastrointestinal bleeding (GI) side effect of aspirin, which reduced iron deficiencies problems such as anemia.
  3. Vitamin B12 – patients with heart disease who take aspirin have been found to have a reduced levels of Vitamin B12.
  4. Vitamin C – Aspirin reduced Vitamin C in the body, taking Vitamin counteracts this effect.
  5. Zinc – Aspirin lowers levels of zinc in the body, so taking zinc counteracts this effect.

3. Discuss three of the six herbs listed that may be helpful for someone taking chemotherapy. Explain why they may be recommended.

The three herbs helpful during chemotherapy are:

  •  Echinacea – is an immune booster during chemotherapy where the immune is compromised due to the chemicals used.
  • Eleuthero – chemotherapy was shown to be less toxic and increased tolerance when used with eleithero. Improves the immune system as shown in studies with women with breast cancer that were treated with chemotherapy and radiation.
  • Milk Thistle – The major flavanoid in milk thistle is silymarin has shown synergistic actions with the chemotherpay drugs cisplatin and doxorubicin. Silymarin offsets cisplatin toxicity on the kidney.

4. Discuss the interactions with herbs and other compounds listed under the Oral Contraceptives heading. Explain why a doctor should be consulted, or why these should be avoided by someone taking oral contraceptives.

Oral Contraceptives (OC) interactions exist with St John’s wort and Tobacco. St John’s wort has been shown to cause intramenstrual bleeding and/or changes in menstrual bleeding. Tobacco used with OC increases the risk five-fold of dying from heart attack and greatly increases the risk of dying from circulatory disease.

5. Discuss the dietary supplements that may be helpful to, as well as the supplement that should be avoided by, someone prescribed tamoxifen.

Useful dietary supplements with tamoxifen are melatonin and tocotrienols. Melatonin together with tamoxifen has been successful in breast cancer, where only tamoxifen usage was unsuccessful. Tocotrienols may enhances the effects of tamoxifen in anti cancer effects but needs further studies.

Citrus flavonoids have shown to interfere with the ability of tamoxifen to inhibit tumor growth therefore should be avoided due to this adversary interaction.

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