Introduction

Summary

Introduction to the Herb Groups Section

introduction:
Physicians, pharmacists and allied healthcare professionals using Interactions™ who are approaching drug-herb interactions without prior familiarity with medicinal herbs may understandably want to use a conceptual model derived from conventional pharmacology to interpret and predict the interactive behavior of herbal remedies.

Herbal medicines do not however generally correspond to a simple pharmaceutical model. Whole herbs, not isolated compounds, are the form used in herbal medicine. Plants are chemically complex, contain many bioactive compounds with synergistic and antagonistic properties such that the activity of whole herb extracts cannot be simply predicted from their constituent parts. Plant compounds often exist as glycosides or natural "pro-drugs", or are complex polymeric/oligomeric molecules of high molecular weight, with pharmacokinetic characteristics quite unlike pharmaceutical drugs. The actions of herbal medicines are correspondingly subtle, multi-faceted and complex, exerting their effects by support and restoration of homeostasis through normalization of intrinsic physiological processes rather than disruption of specific disease mechanisms. Familiarity with herbal medicines requires a familiarity with the plants themselves, and, as Rudolf Weiss, MD, pointed out in his seminal book Herbal Medicine, physicians and medical students wishing to acquire an understanding of the subject must be prepared to develop a personal relationship with the plants they use.
(Weiss RF, 1988. Chapters 1-3.)

In addition, herbal therapeutics do not correspond to the model used in standard practice medicine. Herbal medicine is informed by a holistic viewpoint which has a multifactorial approach to understanding health and disease in which diet, lifestyle, environment and relationship are all evaluated during individual assessment. Polypharmacy is normal, with five or more herbs commonly being combined together in an individuated patient-centered approach to prescription, in contrast with the "take this (drug) for that (condition)" approach.

The "Herb Groups" model in Interactions™ is an artificial classification system that attempts to render numerous medicinal herbs into accessible groupings consonant with a conventional pharmaceutical approach without violating either the complexity of botanical medicines or the therapeutic principles of their employment. 

The Herb Groups are divided into those that may cause pharmacokinetic drug interactions (which may affect the absorption, distribution, metabolism, and excretion of drugs) and pharmacodynamic interactions (which may affect the action or intended effect of drugs). In addition two special groups have been added: Obstetrics and Gynecology, and Chinese Herbs. The Ob/gyn section has few drug-herb interactions but discusses important safety and toxicity issues, while the Chinese Herbs section has been compiled because several major drug-herb interactions, toxicity and adulteration questions have recently received publicity in the scientific and popular literature.

principles and sources:

Herb activities and constituents listed in the Herb Groups section were compiled, adapted and edited from electronic databases including Professor Norman Farnsworth's NAPRALERT database at University of Chicago, Illinois, Dr James Duke's Phytochemical and Ethnobotanical Databases at the Agricultural Research Service and the National Institute of Health's MEDLINE and TOXLINE databases, as well as numerous authoritative textual sources (see literature references to specific Groups.)

• Activities or constituents ascribed to herbs listed in Herb Groups may be based upon widely different assay methods, and may be laboratory, in vitro, in vivo, or human studies-which in turn range from single case reports through placebo controlled trials to metastudies. Neither constituents nor activities are quantified, and interchangeability or even similarity between herbs listed in a given Herb Group cannot be assumed. Even where studies are available to support the classification the data is likely to be non comparable.

• For innumerable medicinal herbs there is a dearth, or often complete absence, of current pharmacological studies: these plants have been assigned to different Herb Groups on the basis of traditional usage in herbal therapeutics, cross checked with authoritative texts, and reviewed by expert authors and educators in the field.

• It follows that many interactions between herbs and drugs remain theoretical or speculative due to lack of supportive pharmacological research, absence of adverse reaction reports, case reports or clinical trials. In all these cases, the general principle followed in the Herb Groups section is to present a classification that provides the healthcare professional or enduser with the highest likelihood of predicting and understanding potential interactions in a clinical context.


Please read the disclaimer concerning the intent and limitations of the information provided here.
Do not rely solely on the information in this article.

The information presented in Interactions is for informational and educational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, case reports, and/or traditional usage with sources as cited in each topic. The results reported may not necessarily occur in all individuals and different individuals with the same medical conditions with the same symptoms will often require differing treatments. For many of the conditions discussed, treatment with conventional medical therapies, including prescription drugs or over-the-counter medications, is also available. Consult your physician, an appropriately trained healthcare practitioner, and/or pharmacist for any health concern or medical problem before using any herbal products or nutritional supplements or before making any changes in prescribed medications and/or before attempting to independently treat a medical condition using supplements, herbs, remedies, or other forms of self-care.



References


Bradley PR, ed. British Herbal Compendium, vol 1. Bournemouth, Dorset, UK: British Herbal Medicine Association, 1992.

Brinker F. Herb Contraindications and Drug Interactions. Second edition. Sandy, OR: Eclectic Institute Inc, 1998.

Fugh-Berman A. Herb-drug interactions. Lancet 2000; 355:134-138.
Abstract: Concurrent use of herbs may mimic, magnify, or oppose the effect of drugs. Plausible cases of herb-drug interactions include: bleeding when warfarin is combined with ginkgo (Ginkgo biloba), garlic (Allium sativum), dong quai (Angelica sinensis), or danshen (Salvia miltiorrhiza); mild serotonin syndrome in patients who mix St John's wort (Hypericum perforatum) with serotonin-reuptake inhibitors; decreased bioavailability of digoxin, theophylline, cyclosporin, and phenprocoumon when these drugs are combined with St John's wort; induction of mania in depressed patients who mix antidepressants and Panax ginseng; exacerbation of extrapyramidal effects with neuroleptic drugs and betel nut (Areca catechu); increased risk of hypertension when tricyclic antidepressants are combined with yohimbine (Pausinystalia yohimbe); potentiation of oral and topical corticosteroids by liquorice (Glycyrrhiza glabra); decreased blood concentrations of prednisolone when taken with the Chinese herbal product xaio chai hu tang (sho-saiko-to); and decreased concentrations of phenytoin when combined with the Ayurvedic syrup shankhapushpi. Anthranoid-containing plants (including senna [Cassia senna] and cascara [Rhamnus purshiana]) and soluble fibres (including guar gum and psyllium) can decrease the absorption of drugs. Many reports of herb-drug interactions are sketchy and lack laboratory analysis of suspect preparations. Health-care practitioner should caution patients against mixing herbs and pharmaceutical drugs.

McGuffin M, et al. (eds.) AHPA Botanical Safety Handbook . CRC Press, 1997.

Weiss RF. Herbal Medicine. Beaconsfield, England. Beaconsfield Publishers Ltd., 1988.