Ginseng, gingko biloba won’t interfere with drug absorption if taken within limit
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June 6, 2007
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CM NEWS - Daily use of ginseng or ginkgo biloba supplements at the recommended doses, or the combination of both supplements, are unlikely to alter the pharmacokinetics of most drugs, a study has found.
Recent findings that the widely-used herbal supplement Saint John’s wort could dramatically affect the absorption and metabolism of many prescription and non-prescription drugs raised concerns that other popular herbal supplements might cause similar changes, thus significantly altering drugs’ therapeutic or toxic effects.
What, for example, about ginseng and ginkgo biloba, two of the most widely used herbal supplements? Ginseng and gingkgo biloba are commonlyly used in traditional Chinese medicine.
What are the effects of ginseng? In Chinese medicine, ginseng (Panax ginseng C.A. Meyer) has long been used as a general tonic or an adaptogen to promote longevity and enhance bodily functions. It has also been claimed to be effective in combating stress, fatigue, oxidants, cancer and diabetes mellitus. Most of the pharmacological actions of ginseng are attributed to one type of its constituents, namely the ginsenosides.
Panax qinsenq & Panax quinquefolium are two species of the ginseng plant. The herb grows to a height of about 60 centimeters (around two feet) and belongs to the Araliaceae family.
The plant grows very slowly and requires a cool shady climate. It grows best in China, Korea, and Japan. Ginseng also grows wild in some parts of North America. Indeed, it has been said that the best type is the wild type with roots which are several years old.
The Asian form is the Panax qinsenq, the American variety is the quinquefolium type. Both have many similar properties, but the Chinese version is more useful for a winter tonic because of its warming nature and the American variety is useful for a summer tonic because it has a more yin or cooling nature
There is an entirely different plant called Eleutherococcus senticosus which, although a botanical cousin of ginseng is often sold as “Siberian Ginseng”. It has some similar properties to ginseng.
Korean ginseng is considered by many folks to be the “best”. The most potent ginseng is considered by some to be that which is grown in South Korea, especially in the Kunsan and Kaesong provinces.
Speaking on May 1 at Experimental Biology 2007, University of Kansas Medical Center scientist Dr. Gregory Reed reports a study that found daily use of ginseng or ginkgo biloba supplements at the recommended doses, or the combination of both supplements, are unlikely to alter the pharmacokinetics – by which drugs are absorbed, distributed, metabolized, and eliminated by the body – of the majority of prescription or over-the counter drugs. Dr. Reed’s presentation was part of the scientific program of the American Society for Pharmacology and Experimental Therapeutics.
The research team, led by Dr. Reed and the late Dr. Aryeh Hurwitz, recruited 72 healthy non-smoking adults (31 men and 41 women, ages 20 to 59) who were not taking any prescription drugs or dietary supplements. The participants were given a “cocktail” of five drugs, each drug in the cocktail chosen because it provides a measure of the activity of a key drug metabolism pathway. Taken together, the five drugs in the cocktail provide measurements of the pathways that determine the pharmacokinetics of over 90% of prescription drugs. The scientists then measured the presence of these drugs or their metabolites in each subject’s blood and urine in order to establish a baseline for how each individual absorbed and metabolized the different prescription drugs in the absence of herbal supplements.
The 72 individuals next were randomly assigned to one of four groups. For four weeks, the first group received a ginseng supplement and a placebo for ginkgo biloba; the second received ginkgo biloba and a placebo for ginseng; the third received both ginseng and ginkgo biloba supplements; and the fourth received placebos for both supplements. The prescription drug cocktail was again administered and blood and urine samples taken in order to determine the absorption and metabolism of these drugs in the presence of either or both of the herbal supplements.
What is gingko biloba used for? According to gingko’s fact sheet provided by the National Centre for Complementary and Alternative Medicine:
- Ginkgo seeds have been used in traditional Chinese medicine for thousands of years, and cooked seeds are occasionally eaten. More recently, ginkgo leaf extract has been used to treat a variety of ailments and conditions, including asthma, bronchitis, fatigue, and tinnitus (ringing in the ears).
- Today, people use ginkgo leaf extracts hoping to improve memory; to treat or help prevent Alzheimer’s disease and other types of dementia; to decrease intermittent claudication (leg pain caused by narrowing arteries); and to treat sexual dysfunction, multiple sclerosis, tinnitus, and other health conditions.
The science behind it: Numerous studies of ginkgo have been done for a variety of conditions. Some promising results have been seen for Alzheimer’s disease/dementia, intermittent claudication, and tinnitus among others, but larger, well-designed research studies are needed.
- Some smaller studies for memory enhancement have had promising results, but a trial sponsored by the National Institute on Aging of more than 200 healthy adults over age 60 found that ginkgo taken for 6 weeks did not improve memory.
- NCCAM is conducting a large clinical trial of ginkgo with more than 3,000 volunteers. The aim is to see if the herb prevents the onset of dementia and, specifically, Alzheimer’s disease; slows cognitive decline and functional disability (for example, inability to prepare meals); reduces the incidence of cardiovascular disease; and decreases the rate of premature death.
- Ginkgo is also being studied by NCCAM for asthma, symptoms of multiple sclerosis, vascular function (intermittent claudication), cognitive decline, sexual dysfunction due to antidepressants, and insulin resistance. NCCAM is also looking at potential interactions between ginkgo and prescription drugs.
In this study, the scientists found no significant differences between those who received one, both, or none of the ginseng and ginkgo biloba supplements in how their bodies absorbed or metabolized any of the five prescription drugs.
This suggests, says Dr. Reed, that neither ginseng nor ginkgo biloba will affect the pharmacokinetics of the majority of prescription or over-the counter drugs.
He does note, however, that the team did not investigate any possible effects of the herbal supplements on pharmacodynamic interactions: the way drugs produce desired therapeutic effects or cause adverse side effects. The possibility of these pharmacodynamic, as opposed to pharmacokinetic, interactions remains to be investigated.
Studies in Dr. Reed’s laboratory continue with an examination of the effects of Saint John’s wort on pharmacokinetics of prescription and non prescription drugs and the role of an individual’s genetic makeup in determining the magnitude of the herbal supplement’s effects. This work was supported by the National Center for Complementary and Alternative Medicine of the National Institutes of Health.