imported>Howard C. Berkowitz |
imported>Howard C. Berkowitz |
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| | date = 21 November 2000 | | | date = 21 November 2000 |
| }}</ref> | | }}</ref> |
| ==Phytochemicals versus plant extracts==
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| Traditional herbalists tend to emphasize the use of either the entire plant, or a simple extract from it, such as a water or [[ethanol]] extract, which explicitly do not attempt to extract specific chemicals. Part of the holistic tradition in many herbal approaches is that Nature provides a complete remedy, and the many compounds in a medicinal plant contribute to its beneficial effects.
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| ===Holistic versus evolutionary models===
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| Evolutionary botanists, however, have questioned why a plant would evolve to have a wide range of substances that specifically benefit humans in an abnormal physiological state. It is not at all unreasonable that a plant might have an evolutionary advantage if it starts to generate a chemical that inhibits some parasite, and this chemical might well inhibit a related parasite in animals.
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| It is less clear why the plant might develop a spectrum of phytochemicals with a synergistic effect, but it is certainly not impossible; there are a number of cases, in medicine, where a prescribed drug is a deliberate combination. For example, several drugs contain an active [[beta-lactam]] antibiotic (e.g., [[ampicillin]]) with another chemical (e.g., [[clavulanic acid]]) that protects the antibiotic from a bacterial resistance mechanisms that destroys the antibiotic.
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| ===The problem of consistency===
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| Few phytotherapies have a longer history, with real benefit, than the use of the foxglove plant, ''[[Digitalis purpurea]]'' for cardiac disease. The plant, which is extremely attractive and is often cultivated as an ornamental, contains potent [[digitalis glycosides]] that support the activity of the heart. These phytochemicals, however, have a narrow margin between the effective dose and the toxic dose. Foxglove plants, grown in different places and times, may have different concentrations of the glycosides, so water extraction (i.e., a tea or [[tisane]]), done in exactly the same manner, may produce more or less active phytochemical because the individual plants vary.
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| For a number of reasons, it has become standard practice to synthesize many plant-derived drugs. One of the most common reasons is to be able to measure the concentration of a single active chemical, and make certain tablets containing it have a constant concentration.
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| Different [#methods of preparation|methods of preparation]] can yield different concentrations. With the foxglove, for example, extracting with [[ethanol|alcohol]] will yield a much higher concentration than will water extraction. Of course, even with water extraction, the concentration can vary if the raw plant is in contact with the water for longer or shorter times. Temperature also affects the concentration extracted into water.
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| ==Paradigms==
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| There is no single paradigm for phytotherapy outside the narrow definition of extracting phytochemicals for conventional medicine. At the very least, there are different traditional Chinese, ayurvedic, and Western paradigms to primary herbalism.
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| ===Western===
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| There are three major sources of information in traditional Western herbalism. Depending on the practitioner, they may be used together, and, indeed, in combination with biomedical approaches. They are empiricism, theories, and revelation.
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| Empiricism and tradition is based on observation by current and past herbalists. It relies on observations that a particular herbal preparation was useful with a particular diagnosis or other indication; it does not assume any particular model.
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| Theoretical models include that of Galen, based on humors. <ref name=Wood2006>{{citation
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| |title =- An Exploration of the Conceptual Foundations of Western Herbalism and Biomedicine With Reference to Research Design
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| |author = Matthew Wood
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| | date = January 2006
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| | publisher = MSc thesis, Scottish School of Herbal Medicine, University of Wales
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| |url = http://www.matthewwoodherbs.com/Dissertation.html}}</ref>
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| ==Availability of plants==
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| Another reason to synthesize a phytochemical is that the plant that contains it is rare. There are real-world cases where meeting the medical demand for a phytochemical could lead to extinction of the plant that produces it. The Pacific [[yew]] tree, ''[[Taxus brevifolia]]'', was found to produce a chemical, [[Taxol]] (brand name) for [[paclitaxel]], useful against breast cancer.<ref name=ForesterYew>{{citation
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| |journal= American Forests
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| | date=July-August, 1991 >
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| | title = The tree that fights cancer - Pacific yew
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| | author = Marshall D. Murray
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| | url = http://findarticles.com/p/articles/mi_m1016/is_n7-8_v97/ai_11012477/print}}</ref> Further investigation showed that it produces a phytochemical precursor for another anticancer drug, [[Taxotere]] brand of [[docetaxel]].<ref name=YewTwo>{{citation
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| | title = FDA Consumer
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| | date = September 1996
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| | title = Second breast cancer drug from yew tree - Food and Drug Administration approves Taxotere, or docetaxel
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| | url =http://findarticles.com/p/articles/mi_m1370/is_n7_v30/ai_18656584/print}}</ref>
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| The tree itself is an endangered species, and it is home to another endangered species, the spotted owl. Ethical conflicts between human, tree, and owl needs have become a popular assignment for learning [[debate]] techniques.<ref name=YewDebate>{{citation
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| | url = http://www.chemheritage.org/educationalservices/pharm/chemo/activity/debate.htm
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| | title = Taxol® and Yew
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| | author = A WebQuest Senate Debate }}</ref>
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| ==Methods of preparation==
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| Obtaining yew-derived drugs is chemically complex. Other plants, such as foxglove or the opium poppy, can have strong effects in humans if the whole plant is eaten, or a simple tea is prepared from them.
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| ==Integrating herbalism with conventional medicine==
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| Since plants do contain chemicals with significant pharmacologic effect, there is a concern with their interacting with conventionally prescribed drugs. Not infrequently, patients may not tell a conventional practitioner about their use of herbals, possibly fearing disapproval. Even if the conventional practitioner does not disapprove, there may be a lack of data about potential interactions; this does not preclude the joint use of herbal and synthetic preparations, but it does call for caution and active monitoring.
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| In a 2002 report, ''Safety of Medicines: A guide to detecting and reporting adverse drug reactions; Why health professionals need to take action''', the [[World Health Organization]] observed "There are differences among countries (and even regions within
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| countries) in the occurrence of" [adverse events], including:
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| <blockquote>the use of traditional and complementary drugs (e.g. herbal
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| remedies) which may pose specific toxicological problems,
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| when used alone or in combination with other drugs.<ref name=WHO-Adverse>{{citation
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| | title = Safety of Medicines: A guide to detecting and reporting adverse drug reactions; Why health professionals need to take action
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| | id = WHO/EDM/QSM/2002.2
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| | author = World Health Organization
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| | year = 2002
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| | url = http://whqlibdoc.who.int/hq/2002/WHO_EDM_QSM_2002.2.pdf
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| }}, p. 9</ref></blockquote>
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| ==Culturally specific phytotherapy==
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| Herbal plant preparations are part of [[traditional Chinese medicine]]. There are many European traditional uses.
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| ==References== | | ==References== |
| {{reflist|2}} | | {{reflist|2}} |
