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Articles > Drug-Herb Interactions: Often overstated

Drug-Herb Interactions: Often overstated

You may sometimes wonder: Does this herbal product interfere with my medication? Parallel to an increase in popularity in herbs, we have also seen an increase in the number of unfavourable reports about herbs and their possible interactions with drugs. It sometimes seems as though these reports are overemphasised by the media, resulting often in the perception that herbs are inherently dangerous. Many reports are based on questionable interpretation of scientific test-tube studies or artificially manipulated preparations, which are not really relevant to how these herbs are used traditionally and in a clinical setting. One has to wonder why popular favourites such as St John's Wort, Kava or St Mary's Thistle, that have been used safely for centuries (if not millennia!) should suddenly become so dangerous that they need to carry a warning or even be banned. Is it a coincidence that it is the most popular and best-selling herbs that are made out to be the greatest threats.

Herbal medicine has been practised safely for centuries while many drugs are relatively new on the market with little known about potential side effects. Therefore, it is inconsistent that in the current medical system herbs are often made out to be the culprit when a side-effect is experienced by a patient. Generallly, drugs as much as they can be life savers - have an inherent problem with toxicity and side-effects. They are scientifically proven to be one of the top five health hazards whilst herbs are classified as safer than food. Risks to the patient are not caused by herbal remedies, but by synthetic drugs with a very small therapeutic range that is easily upset even by consumption of several types of food, semi-luxury beverages and lifestyle products. Butterweck et al (2004) have proven the influence of such innocent foods like broccoli, garlic, pepper, grilled meats and grapefruit on the plasma level of pharmaceutical drugs. The onus of responsibility of safety warnings lies therefore with the actual high risk synthetic drug and not with the commonly used foods and herbs.

Furthermore, whilst it is legitimate to explore unfavourable herb-drug combinations, I do not agree with blanket condemnation of certain herbs without considering the dosage of the herb or the specific herbal preparation used (e.g. Traditional preparation of herbal teas and tinctures or modern extracts and high-dose phytopharmaca). Dosage and preparation are decisive if an interaction or no interaction is rationally to be expected. Traditional preparations, which are low dose whole-herb remedies (and not artificially concentrated extracts) have shown to be safe to use in conjunction with pharmaceutical medication in most cases. Unfortunately, the lack of professional training in herbal medicine by those who work for governing agencies means that these issues are poorly understood and lead to decisions that are neither scientifically nor clinically justified.

The New Zealand Ministry of Health has ordered that the following herbs relevant to the ARTEMIS Herbal Medicine range need to carry a warning. These warnings will be on all of our new labels. The herbs affected are:
- St John's Wort
- St Mary's Thistle
- Licorice

ARTEMIS Herbal Medicine uses traditional preparations. There is not scientific evidence that the dosage used in fresh-plant Mother Tinctures (as in the ARTEMIS Fresh-plant tincture range) and crude herbs (as in the ARTEMIS Therapeutic Herbal Tea range) would be sufficient to interfere with drug medication. For example, Swissmedic (2002/1, p. 7-8), the Swiss Governmental Agency for herbal safety has exempted crude St John's Wort in tea form from herb-drug interactions safety warnings due to a lack of evidence for such concerns.

Apart from the distinction between a traditional and modern preparation a further distinction needs to be made between external and internal applications of a herbal remedy. This can be shown with the example of St John's Wort: Neither in the medical literature nor in clinical practice are there any concerns in regards to the external treatments with St John's Wort (e.g. St John's Wort in an oil or cream base). Therefore topical applications of St John's Wort can be safely used in conjunction with any medication.

This contrasts with highly concentrated St John's Wort extracts (e.g. as tablets) which are not to be taken in conjunction with the following pharmaceutical drugs (as per July 2003):
- Warfarin, Phenproccumon and other anticoagulant medication
- Digoxin (heart medication)
- Indinavir (protease inhibitor used as an anti-retrovirus treatment in HIV-AIDS)
- Cyclosporin (immune suppressive drug for transplant patients)

Inconclusive results exist for
- Theaphylline (Asthma medication). The side effects described in the one and only case report is a common side effect with the drug itself.

Negative results exist for
- Oral Contraceptive Pill. Change in bleeding pattern is common in women on the pill, yet there is no evidence of a mass outbreak of unwanted pregnancies when women concurrently take St John's Wort. Two recent scientific studies confirmed that St John's Wort does not change the hormonal levels or reduce the effectiveness of the pill . All of the women in the trials maintained full protection when concurrently taking a low-dose pill and St John's Wort.

References:
Butterweck V. et al: Pharmaco-kinatic herb-drug interactions. Are preventative screenings necessary and appropriate Planta Med 2004; 70: 784-791.

Pfrunder et al.: Interaction of St John's Wort with low-dose oral contraceptive therapy: a randomised controlled trial. Br J Clin Pharmacol 2003; 56: 683-690.
Hall et al.: The interaction between St John's Wort and oral contraceptive. Clin Pharmacol Ther 2003; 74: 525-535.