Journal of Herbal Medicine
Herbs that can cause hypertension or hypotension can interfere with prescription antihypertensive agents; hypoglycemic herbs can interfere with glycemic control in a patient with diabetes. Some herbs interfere with prescription medications by altering their metabolism. For example, Eucalyptus can induce microsomal liver enzymes 51 while flavonoids from Echinacea purpurea are known to inhibit the cytochrome PA4 and sulfotransferase drug-metabolizing enzymes.
Not only might herbal therapy be toxic, but using an herbal remedy over a proven conventional therapy can be dangerous, too. Many oncologists have seen patients with early-stage cancers who eschewed curative conventional care in favor of herbal medicines. After these herbal treatments failed, the patients returned to the oncologists with incurable metastatic diseases.
In fact, studies 54 have shown that patients who use herbs and other alternative therapies are more likely to abandon potentially beneficial conventional therapy when faced with an illness. Patients may also continue detrimental behaviors, such as smoking tobacco or drinking large amounts of alcohol, with the rationalization that the herbal remedy they are taking will be protective. An herb that may be safe in small doses may become dangerous in higher doses.
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The risk of overdose is higher in herbal preparations than conventional medicines because of the already mentioned product variability. Consider the patient who assumed if "some is good, more is better" with respect to a copper-containing supplement he was taking. As he began to feel worse, he increased the dose. By the time he came to the attention of conventional health providers, he was unable to eat and was wasted and jaundiced, and had acquired Wilson disease.
However, herbs in extract form are often much more potent than the traditionally used form, and can be harmful Table 3. Of the 20, available products, which is the physician most likely to encounter? A survey of US health food retail stores revealed that the top 10 selling herbs were echinacea Echinacea pur purea and angustifolia , garlic Allium sativum , goldenseal Hydrastis canadensis , ginseng Asian Panax ginseng and American Panax quinquefolius , ginkgo Ginkgo biloba , saw palmetto Serenoa repens , aloe Aloe species , ma huang Ephedra sinica , Siberian ginseng Eleutherococcus senticosus , and cranberry Vaccinium macrocarpon.
Patients decide which herbs to use in a variety of ways. Because of the requirements that herbal medicines must not directly claim cures on the label, manufacturers have become creative with marketing. Patients also get information through word of mouth, encouraged by anecdotal reports from friends. An herbalist who has training in the use of plants for healing may be consulted. Advice can be found from health food store workers. An undercover FDA study asked clerks what to buy "for my immune system," "high blood pressure," or "something that works on cancer.
Combination products with names like "Immunace," "Immunaction," or "Immunectar" were most frequently recommended; ginseng-containing products were recommended second and were the most expensive. Pharmacists, on the other hand, are unlikely to give specific recommendations on herbal products sold in their stores, and say they do not know much about them.
People can also explore the Internet to discover information about herbs. Internet sources are often perceived as "published" and therefore entirely factual. However, most sites merely list herbs and their uses, few mention regulations, safety, or efficacy. Even an herb with well-recognized toxicities, such as ephedra, may have no cautionary statement. A few sample Web sites are listed below:. American Botanical Council: A respected organization dedicated to dissemination of factual herbal information.
Herbal Information Center: Brief overviews on common herbs; few warnings; mostly geared to sell. HerbNet: Links to other herb sites; mostly advertisements but some good information can be found.
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Herbal Resource Inc: Primarily a sales site but occasionally references are noted. Biased and misleading, even stating that "there are no side effects from herbs. When patients or practitioners want nonbiased information on a commonly used herb, they are advised to buy a book that bases advice on published and critically reviewed literature. A comprehensive literature search will ensure the most scientific, peer-reviewed information is being reviewed, but this process is often time consuming and, thus, impractical. Beginning in , the German equivalent of the FDA went as far as to publish a series of herb recommendations, the Commission E Monographs, which detail dosages and indications for herbs whose efficacy is supported by the literature, and these have recently become available in the United States.
However, the extrapolation of these European findings usually conducted with well-characterized, pharmaceutical herbal preparations to herbs available in the United States is complicated by the relative lack of regulatory standards in this country, as described earlier. The great variation in US herb quality is unfortunate in light of the known pharmacological actions in humans of well-characterized botanical preparations. If one can put the question of US regulation aside, comments can thus be made on the efficacy of some of the best-selling herbs mentioned above.
Valerian Valeriana officinalis ranks as one of the most well characterized of the widely used herbs. Listed in The National Formulary until , valerian has been described in human studies as possessing sedative and anxiolytic activity 56 and is often combined with other sedative herbs like hops Humulus lupulus. In the case of Ginkgo biloba , which contains ginkgolides that antagonize platelet-activating factor, human studies were greatly facilitated by the availability of a high-quality extract EGb from the manufacturer, Willmar Schwabe, in Karlsrube, Germany.
The efficacy of Ginkgo biloba extract in improving or delaying cognitive deficits was recently demonstrated in a multicenter US trial of patients with early-stage Alzheimer dementia. Improvements in 2 of 3 clinical parameters of cognitive function were observed as early as at 12 weeks of Ginkgo extract, Egb , when compared with placebo. Ginseng is another widely used herb touted in Chinese traditional medicine as an "adaptogen" that allows the body to respond to physical and emotional stress.
The best data to date support a role for ginseng as a vasodilator and in serving a cardioprotective role in the presence of oxygen free radicals. For the practicing internist, the most interesting data come from efficacy comparisons between herbs and prescription medications. For example, limited data suggest that saw palmetto compares favorably with finasteride in the management of benign prostatic hyperplasia. The wisdom of herbal self-treatment, as is often the case in the United States, is discussed in the following section, along with more information about specific herbs the internist is likely to encounter.
Given the previously detailed shortcomings of herbal preparations in the United States, the question arises whether any herbs possess pharmacological activity distinct from prescription or over-the-counter drugs that might therefore warrant their cautious use. Such herbs are few. The most commonly used herb in the United States and Europe, Echinacea purpurea, may be one. Unlike over-the-counter decongestants or antihistamines, alkylamide and polysaccharide constituents of echinacea possess significant in vitro and in vivo immunostimulation due to enhanced phagocytosis and nonspecific T-cell stimulation.
One well-designed, double-blind study randomized patients with acute flulike illness to an echinacea extract or placebo and showed that echinacea decreased the duration of symptoms from 10 to 7 days. Neither study used commonly available preparations of echinacea. Most herbs fall into the category of agents that share pharmacological mechanisms of action with already existing prescription or over-the-counter drugs.
Based on a logical consideration of the current state of herb standardization and pharmacokinetic evaluation, the patient would be best steered toward a regulated pharmaceutical preparation capable of a predictable pharmacological response. For example, powdered ginger root has been tested in humans for prophylaxis against motion sickness compared with dimenhydrate Dramamine. Other examples of herbs possessing actions similar to existing, regulated drugs are feverfew for migraines, 64 valerian for anxiety, 65 and garlic for hypercholesterolemia.
Of greater concern to the physician is when patients use herbs with redundant pharmacological activity for diseases not recommended for self-treatment. Miller 67 heightened the public's awareness of the antidepressant actions of St John's wort, an herb containing the potential monoamine oxidase inhibitor hypericin. While St John's wort has shown promising antidepressant action, 60 it is unlikely that patients can make a diagnosis of endogenous depression, much less differentiate their condition from medical conditions mimicking depression.
In addition, there remains concern for hypertensive reactions resulting from concomitant ingestion of high tyramine-containing foods and St John's wort, and hypericin is well known to cause photosensitivity. Similarly, the use of saw palmetto for benign prostatic hypertrophy presents another dilemma. Herbal remedies are commonly used by patients who access conventional health care.
Few have been shown to have beneficial effects beyond those of conventionally regulated products, and they may be costly, adulterated with dangerous additives, inherently toxic, or cause the patient to forgo potentially curative care. All medicines can be toxic under specific circumstances; there is always a risk that an adverse reaction will present a hazard to a patient. With licensed medicines, however, regulations ensure the risk is small and monitor the medicine's efficacy, safety, and quality. No such controls over herbal medicines exist. If a patient presents with a problem that might be due to an herb, the physician should discontinue the product and watch for resolution.
Botany departments at major universities can also be a source of information. If patients ask if "herbal medicines" in general are safe or effective, they should be counseled about the lack of regulations for quality, safety, or efficacy, the differences in preparations from different manufacturers, and the lack of mechanism for reporting adverse effects. Curious patients can be directed to read the books mentioned, and cautioned against biased information that they may receive from health food store employees, pamphlets shelved near herbs, and the Internet.
If patients mention a friend who was helped by a certain remedy or an advertisement that was seen depicting a dramatic success with a certain herb, they should be counseled on the dangers of anecdotal reports. Patients take our recommendations of conventional medicines because we suggest it, not because we present them with reams of data from randomized controlled trials; thus, it is not unexpected that their approach to the use of unconventional medicine is the same.
Patients with chronic conditions such as AIDS or cancer should also be warned that some of the adverse effects of herbals are often similar to symptoms of problems associated with their disease or treatment, thus making it difficult to discern if the disease or the "remedy" is the problem. Classically trained physicians cannot ignore herbal medicines anymore.
We must realize that patients are using herbal medicines, and insurance companies are beginning to cover the costs and are even asking us to oversee the use of herbs in certain situations. We must all become educated about these products, and at the very least know where to find information when we need it.
Asking patients about supplement use during the initial history is thus imperative. Patient disclosure of herb use may provide an opportunity for the physician to redirect the patient toward effective conventional health care.
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By taking a complete drug and supplement history, a dialogue can be initiated to rationally compare the appropriateness of herbal remedies and regulated pharmaceuticals in relation to the severity of the condition. Until herbs in this country are more strictly regulated, however, no classically trained physician should recommend an herbal product to a patient. For the herb-using patient who views conventional medicine with ambivalence, the physician can foster a more open and communicative relationship by demonstrating an objective understanding of both alternative and conventional approaches.
All Rights Reserved. Regulation: dietary supplement and health education act Quality control Efficacy and safety studies Toxicities Commonly used herbs Pharmacological basis for use or avoidance of herbal medicines Conclusions Article Information References. View Large Download. Table 1.