We are seeing increasing evidence that the use of complementary/alternative medicine (CAM) in North America is on the increase. Dr. David Eisenberg ,who surveyed 1539 adults in 1991 and 2055 adults in 1997, found that the use of CAM had increased from 33.8 % to 42.1 % of the population over a seven year period. While this constitutes a 25 % increase there are certain segments or sectors of the CAM pie that have grown much more rapidly. In particular the use of high-dose vitamins has grown 130% and the use of herbal supplements has grown 380% between 1990 and 1997. Of special interest is the fact that the majority of patients don't tell their physicians about their use of CAM in general and supplements in particular. Almost one in five patients taking prescription medicines are also taking herbs, high-dose vitamins, or both. This means that there are about 15 million adults in the USA who are at risk for potential interactions between their medicines and supplements. Some of these interactions are relatively benign while others can be potentially life threatening. 

The number of possible interactions between supplements and medications is overwhelming. Interactions can occur by several different mechanisms including: decreased absorption of medication due to more rapid transit time; decreased absorption of medication due to binding; increased or decreased medication levels due to altered metabolism of medicine caused by changes in enzymatic activity; increased or decreased effectiveness of medication by a supplement with similar or opposite biochemical/physiologic effects; and increased chance of medication toxicity with supplements that share a similar side effect profile. One way of identifying the most common potential interactions is to compare the most commonly prescribed medicines and the most commonly consumed supplements. Another way of approaching this problem is to look at those medicines which have a narrow "therapeutic window," control potentially life threatening conditions, or are notorious for side effects or interactions and identify which supplements could alter this delicate balance and lead to dangerous complications. 

If we are to "above all do no harm" and help our patients to not harm themselves the latter approach is probably more practical and more worthy of our attention. The drugs and classes of drugs which have a narrow therapeutic window* (and for which we usually don't want generic substitutes), control potentially life threatening conditions, or are notorious for toxicity or interactions include: antiarrhythmics (particularly digitalis*), antiasthmatics (particularly theophylline*), anticoagulants (particularly coumadin*), anticonvulsants*, antidepressants (particularly MAOI), antihypertensives, hepatotoxic agents, immunosuppressants and nephrotoxic agents. 

Examples of a few common supplements which could cause problems with the categories listed above are: 

Antiarrhythmics beware aconitine (larkspur, monkshood), foxglove, oleander, hawthorn, Siberian ginseng, glycyrrhizin (licorice), ephedra/Ma huang, guarana, kola, coltsfoot, devil's claw, fenugreek, fumitory, ginger, yohimbe, lobelia, blue cohosh, jimsonweed, belladonna.
Antiasthmatics beware ephedra/Ma huang, guarana, kola, yohimbe, licorice. 

Anticoagulants beware alfalfa, angelica, aniseed, arnica, bogbean, cassia, chamomile, clove, fenugreek, ganoderma, isatis, shitaake, tremella, pau d'arco, dong quai (tang-kuei), vitamin E, dan-shen (salvia), celery, feverfew, fucus, garlic, ginger, ginkgo, ginseng, horse chestnut, horseradish, licorice, meadowsweet, melilot, poplar, prickly ash, quassia, red clover, sweet woodruff, tonka beans, willow (cinchona bark), agrimony, goldenseal, mistletoe, yarrow, chondroitin sulfate.
Anticonvulsants beware wormwood, sage, GLA (evening primrose oil, borage oil), Shankapulshpi, ephedra/Ma huang. Antidepressants beware ginseng, ephedra/Ma huang, passion flower, St. John's wort, yohimbe, guarana, kola, lobelia, blue cohosh, broom, glycyrrhizin (licorice).
Antihypertensives beware ginseng, yohimbe, guarana, kola, ephedra/Ma huang, lobelia, blue cohosh, broom, devil's claw, goldenseal, squill, hawthorn, astragalus, codonopsis, prunella, scrofularia, salvia.
Hepatotoxic Agents beware, chaparral, comfrey (boneset, knitbone, Symphytum officinale), pennyroyal (Mentha pulegium, Hedeoma pulegioides), germander, borage, senecio, coltsfoot, mistletoe. 
Immunosuppressants beware echinacea, goldenseal, astragalus, glycyrrhizin (licorice, Sho-saiko-Tok, Sai-boku-To, Sairei-To), alfalfa, pau d'arco, zinc. 
Nephrotoxic Agents beware aristolochic acid (snakeroot, Stepania tetrandra, Magnolia officinalis), burdock, astragalus, peony, dandelion, glycyrrhizin (licorice). 

In an industry that is virtually unregulated it is also important to be able to help patients identify the more reputable supplement manufacturers for reasons of both efficacy and safety. The kinds of things to look for on a supplement bottle are: the milligram dose of each ingredient; the percentage of active ingredient(s); an expiration date; a phone number to call for questions; dosing instructions; and warnings about potential side effects. If the bottle has this information and the company is also able to provide product specific research studies and independent laboratory assays documenting contents then you are probably dealing with a more reputable manufacturer. Try to steer patients away from using products from companies that don't meet these criteria. 

There are many texts and web sites you could go to for further information on interactions between herbal products and medications. One of the better resources I've found so far is the book by Francis Brinker "Herb Contraindications and Drug Interactions" which is available from the Eclectic Institute (503-667-4120) for about twenty dollars. 

With the dramatic increase in the use of supplements by our patients we need to routinely ask about this on our medical histories and be prepared to advise patients on potentially dangerous interactions. To do otherwise is truly a recipe for disaster.