[PHNUTR-L] St. John's wort, Echinacea interfere with some drugs by moving them out of the body too fast

[Kathrynne Holden, MS, RD]

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Public release date: 4-Apr-2006
http://www.eurekalert.org/pub_releases/2006-04/foas-sjw032206.php

Contact: Sylvia Wrobel
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770-270-0989
Federation of American Societies for Experimental Biology

St. John's wort, Echinacea interfere with some drugs by moving them out 
of the body too fast

St. John's wort and Echinacea, two widely-used herbal preparations, have 
been found to increase activity of a specific enzyme in the liver and 
intestine, an enzyme involved in the metabolization of roughly one in 
every four pharmaceutical drugs on the market today, reports a clinical 
pharmacologist at Indiana University School of Medicine.

Metabolizing pharmaceuticals too slowly or too quickly can cause drug 
toxicity and/or loss of therapeutic function. Drugs known to be affected 
range from oral contraceptives to antihypertension medications to drugs 
to prevent rejection of transplanted organs.

Dr. J. Christopher Gorski described his research and its clinical 
significance on April 4 at Experimental Biology 2006 in San Francisco. 
Dr. Gorski was one of several experts speaking at a symposium on 
metabolic considerations in the action of herbal medicines, part of the 
scientific program of the American Society for Pharmacology and 
Experimental Therapeutics.

The fact that St. John's wort causes many drugs to be metabolized too 
quickly was well established when Dr. Gorski began his research. He 
wanted to know how it happened. In order to prove that the process 
involved enzyme cytochrome P450 3A4, he worked with patients who had 
been taking the herbal preparation before they were given midazolam 
(Versed), a relaxant often given to patients before minor surgical 
procedures. Midazolam was chosen because it is one of the 
pharmaceuticals known to be metabolized by that particular enzyme. 
Laboratory analysis revealed the relaxant metabolized much more quickly 
in patients who had been using St. John's wort.

The team then turned to oral contraception, following up on clinical 
reports that St. John's wort had reduced the efficacy of these drugs. 
Dr. Gorski found that one or more components of the oral contraceptive 
were more rapidly metabolized and cleared from the body by cytochrome 
P450 3A4 in women who also had been taking St. John's wort. Furthermore, 
when 12 women who had not been taking St. John's wort added it to their 
drug regimen for two months, seven of 12 women experienced increased 
breakthrough bleeding, generally considered a clinical indication of 
decreased protection against pregnancy by the oral contraceptive.

Dr. Gorski now is studying the impact of St. John's wort on 
antihistamines and other pharmaceutical drugs.

Dr. Gorski began his research with Echinacea, a herbal preparation often 
touted for its ability to prevent or treat colds and flu, simply because 
it is one of the most commonly used herbal preparations in the country. 
Unlike as with St. John's wort, there had been no reports in the 
scientific literature of problems caused by Echinacea's interaction with 
pharmaceutical drugs. But when he administered the recommended doses for 
the recommended eight days to individuals taking various 
pharmaceuticals, he found that Echinacea altered the metabolic capacity 
of a number of enzymes that play important roles in the de disposition 
of these medications. He now is looking at Echinacea's impact on other 
commonly used pharmaceuticals.

Bottom line? Dr. Gorski says that patients and clinicians should be 
aware of possible reductions in systemic bioavailability – and thus 
lowered therapeutic efficacy – of conventional drugs when taken at the 
same time as St. John's wort, Echinacea, and possibly other herbal 
preparations. And when he says conventional drugs, he means both 
prescription and over the counter ones. Acetaminophen, for example, one 
of the most commonly available OTC drugs, used widely for muscle pain, 
inflammation and headaches, is extremely safe but can have extremely 
harsh consequences if it is altered. A "doomsday prediction" would be 
the arrival on the market of some new herbal preparation that would 
impact such a widely used drug.
-- 
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
"Ask the Parkinson Dietitian"  http://www.parkinson.org/
"Eat well, stay well with Parkinson's disease"
"Parkinson's disease: Guidelines for Medical Nutrition Therapy"
http://www.nutritionucanlivewith.com/