| Home | Tools: Save | Print | E-mail | Most Read |
| The Essentials of Traditional Chinese Herbal Medicine |
| Adjust font size: |
(1) A Brief History of the Development of TCD Traditional Chinese pharmacology, pharmacology in the broad sense, is an important integral part of traditional Chinese medicine (TCM). It deals with the origin, collection, processing, actions and uses of traditional Chinese drugs (TCD), or Chinese materia medica, under the guidance of the basic theory of TCM. There are very rich resources of TCD. According to a recent survey, the number of TCD is 12,807. Among them, 11,146 are drugs of plant origin; the rest are of animal or mineral origin. Hence, traditional Chinese pharmacology is sometimes called traditional Chinese herbal pharmacology. Beginning in the 1920s, modern Chinese pharmacologists started to study the actions of TCD in terms of modern medical science. Since the 1950s, there has been an increasing number of Chinese pharmacologists and related scientists engaged in the study of TCD. Chemical ingredients and fractions have been isolated from a large number of TCD, and their actions have been studied. (1) A Brief History of the Development of TCD In ancient times, people came to realize that some plants and animal parts had dramatic effects when consumed by humans, such as causing vomiting, perspiration, diarrhea, etc. There was a legend that 4,000 years ago there was an emperor called Shen Nong (shen means god; nong means agriculture), who devoted himself to the development of agriculture. He tasted hundreds of plants to find out if they were fit to eat, in the process discovered many plants with pharmacological effects. Hence, the name of the first classical work on Chinese materia medica, published around 1,800 years ago, was attributed to him, and known as Shen Nong’s Herbal Classic (Shen Nong Ben Cao Jing). It contains details of 365 drugs. Various methods of processing of these natural drugs were developed and summarized in a book named Lei’s Treatise on the Preparation of Drugs (Lei Gong Pao Zhi Lun), written by Lei Xiao around 1,500 years ago. It was the first book of its kind. After processing, either the effectiveness of the processed drug increased or its toxicity decreased. The number of TCD increased steadily as the years went by. In the Tang Dynasty (618-907), for the first time the government published (in 659) a book on TCD named The Newly Revised Materia Medica (Xin Xiu Ben Cao) or The Tang Materia Medica (Tang Ben Cao), which included details of 850 drugs, many of them were illustrated. Fifty years later, a book named Dietetic Materia Medica (Shi Liao Lei Ben Cao), written by Dr Meng Xian on drugs used as food, was published. In the Song Dynasty (960-1279), Dr Tang Shenwei edited Classic Classified Materia Medica for Emergencies (Jing Shi Zheng Lei Bei Ji Ben Cao), or the Classified Materia Medica (Zheng Lei Ben Cao), which listed 1,746 drugs and had many useful prescriptions attached. In the Ming Dynasty (1368-1644), a monumental work on materia medica, Compendium of Materia Medica (Ben Cao Gang Mu), was compiled by the great doctor and pharmacist Li Shizhen and published in 1590. In 52 volumes, it contained details of 1,892 drugs, 1,160 pictures and 11,096 prescriptions. This was a multidisciplinary book of botany, pharmacognosy, pharmacology and therapeutics. The Chinese Materia Medica Dictionary, published in 1977, contained details of 5,766 drugs, while the Glossary of Chinese Materia Medica, published in 1993, contained details of 8,488 drugs. A recent survey found that the number of TCD has now been raised to 12,807, among which 11,146 are drugs of plant origin, 1,581 are drugs of animal origin, and 80 are mineral origin. (2) The Development of Modern TCD Pharmacology The modern pharmacology of TCD started in China 70 years ago, when Dr KK Chen (Chen Kehui) published a paper on ephedrine. There were around 30 TCD studied from the 1920s to the 1940s by phytochemists and pharmacologists, such as danggui (Radix Angelicae Sinensis), huanglian (Rhizoma Coptidis), chuanwu (Radix Aconiti), changshan (Radix Dichroae), fangji (Radix Stephaniae Tetrandrae), beimu (Bulbus Fritillariae), yanhusuo (Rhizoma Corydalis), etc. Beginning in the 1950s, the government has paid great attention to the development of TCM. TCM colleges have been established in every province and autonomous region, and TCM hospitals and research institutes at the national, provincial, municipal and even county level have been set up. The development of TCM has thus entered a new era. The trend of development of TCD is in two directions: One treats TCD as ordinary natural resources, plants and/or animals, and endeavors to extract new chemical ingredients from them. A number of compounds have been isolated and identified. Their actions have been studied and they have undergone clinical trials. Hence, a number of new drugs have been developed and marketed, such as tetrandrine, tetramethylpyrazine, artemisinine and its derivatives, ferric acid, etc. The other is the study of TCD under the guidance of TCM theory, mainly studying the actions of prescriptions experimentally and clinically. The traditional pharmaceutical preparations are also undergoing transformation. New forms of patent TCD are instant powders, tablets, injections and capsules. In order to elucidate the actions of prescriptions, both classical and contemporary, actions of drugs in the prescription individually and in combination have been studied and clarified. Chemical constituents in prescriptions are also being investigated. Hence there is both a need and the conditions to form a modern pharmacology of TCD which will include both the classical descriptions of actions and uses in TCM and the new information and data obtained from the study of TCD using modern technology and expertise. As a result, since the 1980s, the pharmacology of Chinese materia medica has been listed as a course in the curriculum of colleges of TCM, and textbooks have been published. Yet, TCM pharmacology is still at the infant stage, and there is still a lot of work to be done. TCD consist of natural substances, such as plants, whole or parts of animals, and minerals. As stated above, drugs of plant origin are the main part of TCD. Their species, habitat, collection and storage are important factors determining their quality and therapeutic effectiveness. 3.1 Varieties of TCD 3.2 Habitat of TCD 3.3 Collection of TCD In general, a drug consisting of leaves or an entire herbaceous plant should be collected when its flowers are in full boom. For example, the total alkaloid content in Herba Leonuri when its flowers are in full bloom is 1.26 percent, while it is 0.39 percent when its fruits are ripe. Most drugs from flowers should be collected when the flowers are blooming. But some of them should be collected when the flowers are still in bud. For example, the content of rutin in the flowers of the Chinese scholartree is 13 percent, while in the buds it is 23.5 percent. Drugs from fruits are usually collected when the fruits are ripe. But some such drugs should be collected when the fruits are immature, for example, immature bitter orange and Tibet Fructus Canarii. Drugs from roots or rhizomes should be collected in late autumn or spring. Drugs from bark should be collected in spring or early summer. As TCD are drugs of plant, animal or mineral origin, they are natural products, and should be processed before being taken as drugs. 4.1 The purpose of processing: 4.1.1 To increase potency, and hence effectiveness 4.1.2 To alleviate potency, or minimize or eliminate side effects or toxicity 4.1.3 To change the action or site of action of drugs 4.1.4 To make the drugs easier to prepare or store 4.1.5 To clear away unwanted substances such as grit, unpleasant odors, etc. 4.2 Methods of processing 4.2.1 Physical processing 4.2.2 Liquid processing 4.2.3 Fire processing 4.2.4 Processing by both water and fire (5) The Properties and Actions of TCD 5.1 The four properties These are cool, cold, warm and hot. In TCM, diseases are classified into two major categories, that is, cold and hot. Drugs that can treat cold diseases are assigned warm or hot properties; drugs that can treat hot diseases are considered to have cool or cold properties. Cool or cold, and warm or hot are just a matter of difference in strength. Cool is weaker than cold, and warm is not as strong as hot. Drugs with cool or cold properties usually have such actions as “clearing away heat and toxic materials”, “removing heat from blood”, “nourishing yin” and “purging fire”. In addition, drugs with warm or hot properties can warm the interior, dispel cold, support yang and replenish qi. In terms of yin and yang, cool and cold belong to yin, and warm and hot belong to yang. Clinical studies of body temperature, heart rate, blood pressure, respiratory rate, and amount of saliva secreted have shown that most patients with hot diseases show a hyper-reaction of the sympathetic nervous and adrenergic system, while patients with cold diseases usually show a hypo-reaction of this system. When patients with hot diseases are treated with cold drugs, not only are their feverish symptoms relieved, but there is a decrease in the heart rate, amount of catecholamines and 17-hyroxycorticoids excreted in the urine. The very opposite occurs when patients with cold diseases are treated with hot drugs. These effects of cold and hot drugs have also been verified by experiments. Experiments have also shown that warm and hot drugs can increase the oxygen consumption of rat tissues, carbohydrate metabolism and amount of water taken. They can postpone the onset of death in a cold environment and slow the decrease of body temperature. Cool and cold drugs have the opposite effects. There is evidence that warm and hot drugs can promote the metabolic process, while cool and cold drugs can inhibit it. It has been found that cold drugs usually have tranquilizing, sedative, analgesic or anti-convulsant actions, while warm drugs usually stimulate the central nervous system. Cold drugs usually have anti-microbial, anti-inflammatory and anti-toxin actions. Some even have anti-tumor actions. 5.2 The five tastes Traditionally, TCD have been regarded as having five kinds of tastes, i.e. pungent, sweet, sour, bitter and salty, although some drugs may be stringent or tasteless. Nonetheless, the five tastes are standard. Clinical practice has found that each kind of taste is closely related to the relevant drug’s therapeutic capability. 5.2.1 Pungent taste Pungent drugs have an activating or pushing action to promote the flow of qi and the circulation of blood. Pungent drugs possess the action of moistening tissues, because they can promote the circulation of blood. Pungent drugs can cause dryness, which leads to exhaustion of qi and yin, due to their dispersing action. Hence, they should be used with care to treat patients with deficiency of qi and yin or deficiency in the exterior with hyperhydrosis (excessive perspiration). 5.2.2 Sweet taste They are mostly drugs with tonifying effects. For example, ginseng and Astragalus (huangqi), with sweet and warm properties, are qi tonics, and Radix Glehnia (bei shashen) and Radix Ophiopogonis (maidong), with sweet and cold properties, replenish yin. Drugs such as licorice and honey, with a sweet taste, can regulate the actions of drugs combining together or relieving spasms and pain. Some sweet drugs can moisten the lungs to resolve phlegm, and moisten the intestines to relieve constipation. 5.2.3 Sour taste 5.2.4 Bitter taste 5.2.5 Salty taste 5.2.6 Astringent taste 5.2.7 Tasteless drugs In TCD, every drug has both property and taste. Hence, in clinical use the property and taste of a drug should be considered together in treating diseases. 5.3 Ascending and descending, floating and sinking These are peculiar properties of drugs stated in TCM to show the inclination and direction of their action. Ascending and floating indicate that the action of the particular drug is going upward or outward within the body, while descending and sinking imply going downward and inward. These activities will counteract pathologic actions which are going in the opposite directions. The drugs with ascending and floating actions are drugs elevating the yang, dispelling pathogenic factors from the exterior of the body, expelling coldness and causing vomiting. Drugs with descending and sinking actions are drugs with the properties of clearing away heat, catharsis, inducing diuresis, checking perverted flow of qi and relieving asthma. The properties of ascending and descending, floating and sinking are closely related to the properties and tastes, processing and compatibility of drugs in a prescription. For example, most ascending and floating drugs have pungent or sweet tastes and warm or hot properties, while descending and sinking drugs have sour, bitter or salty tastes and cool or cold properties. Drugs processed with alcohol will become lifting; with salt will become laxative; with ginger will become dispersing; and with vinegar will become astringent. Dahuang (Radix et Rhizoma Rhei) has a bitter taste and cold property, which is descending, and is used to treat constipation. But if it is processed with liquor, dahuang will clear away heat and toxic materials, and can be used as an antibiotic and antipyretic agent. The action of drugs can be modified by combination with other drugs. For example, chenpi (Pericarpium Citri Reticulatae, tangerine peel) acts as a tonic if used in combination with tonic drugs, as a purgative when combined with purgatives, and will be ascending when combined with ascending drugs and descending when combined with descending drugs. Some drugs act as agents to float other drugs upward, e.g., jiegeng (Radix Platycodi, ballonflower); while niuxi (Radix Achyranthis Bidentatae) can make other drugs sink. (6) Meridian Classification (Guijing) of TCD The classification of TCD according to meridians, or guijing, means that each drug has a selective action manifested on one or several specific meridians. In TCM, meridians are closely connected with the internal organs (zang and fu). Hence, drugs are grouped or classified, for instance, as drugs of Lung Meridian of Hand Taiyang (LU), Stomach Meridian of Foot Yangming (ST), etc. This classification is helpful for choosing drugs to treat disorders of particular organ(s). According to studies of pharmacological actions using modern pharmacological methods, the guijing of a particular drug is manifested in line with its pharmacological actions. For example, in TCM the organ gan (liver) is considered as “determining the conditions of tendon” and “endogenous wind marked by vertigo, spasms and convulsions are related to gan.” There are 22 drugs having anti-spasm and anti-convulsive actions, classified as belonging to the Liver Meridian of Foot Jueyin (LR). In TCM, the large intestine is considered an organ for passing wastes. There are a number of drugs classified as belonging to the Large Intestine Meridian of Hand Yangming (LI), having a purgative action. Fei (lungs) is an organ in charge of qi, performing the function of respiration and storing sputum. Drugs classified as belonging to the Lung Meridian of Hand Taiyin (LU) have antitussive, expectorant and antiasthmatic actions. Therefore, guijing really means the site of action of drugs on particular organs. In terms of toxicity, TCD can be classified as non-toxic, slightly toxic, moderately toxic and extremely toxic. In the ancient literature of TCD, it is stated that no drugs is non-toxic if it is taken in excessive doses or over too long a period of time. In short, when TCD are used to treat disease, all the properties, actions, tastes and toxicity should be considered at the same time. Then TCD are chosen according to the zheng (syndrome or syndrome-complex). (8) Compatibility and Incompatibility of Drugs in a Prescription In clinical practice, traditional Chinese medical doctors usually prescribe around ten or more TCD to make a formulation, based on overall analysis of patients’ symptoms and signs (zheng). It is important to determine whether or not the drugs in the formulation are compatible with each other and how they interact with each other. 8.1 First of all, there are four categories of drugs in a prescription, namely, the principal, adjuvant, auxiliary and conductant drugs. The principal drug(s) provides the principal curative action. The adjuvant drug(s) strengthens the action of the principal drug(s) and treats the secondary symptoms. The auxiliary or correctant drug(s) is used to relieve minor or secondary symptoms or to temper the action of principal drug(s) when the latter is too potent. The conductant drug(s) directs the action to the affected meridian or site. Drugs in a prescription interact with each other in the following six ways: (1) mutual reinforcement: two drugs having similar properties and actions reinforce each other; (2) assistance: two more drugs in a prescription with one as the principal drug and the rest playing an adjuvant role; (3) mutual restraint: different drugs weaken or neutralize each others’ actions; (4) neutralization: one drug neutralizes the side effects of another drug; (5) counteraction: one drug antagonizes the therapeutic action of another drug; and (6) incompatibility: two drugs put together will result in enhanced side effects or toxicity. 8.2 Based on the interactions of drugs in a prescription, some incompatibilities occur when combining drugs. There are the so-called 18 incompatible medicaments and 19 medicaments of mutual restraint. The 18 incompatible medicaments are as follows: Radix Glycyrrhizae (gancao) is incompatible with Radix Euphorbiae Pekinensis (daji), Flos Genkwa (yuanhua), Radix Euphobiae Kansui (gansui) and Sargassum (haizao); Radix Aconiti (fuzi) is incompatible with Bulbus Fritillariae (beimu), Fructus Trichosanthis (gualou), Rhizoma Pinelliae (banxia), Radix Ampelopsis (bailian) and Rhizoma Bletillae (baiji); Radix Veratri Nigri (lilu) is incompatible with Radix Ginseng, Radix Salviae Miltiorrhizae (danshen), Radix Adenophorae and Radix Glehniae (nan shashen and bei shashen), Radix Sophorae Flavescentis (kushen), Radix Scrophulariae (xuanshen), Herba Asari (xixin) and Radix Paeoniae (shaoyao). If the above-listed drugs are put together in a formulation, it is said that there will be serious side effects. The 19 medicaments of mutual restraint are as follows: Sulphur restrains crude sodium sulfate; mercury restrains arsenic trioxide; Radix Euphorbiae Ebracteolatae (langdu) restrains litharge; Semen Crotonis (badou) restrains Semen Pharbitidis (qiannuzi); Flos Caryophylli (dingxiang) restrains Radix Curcumae (yujin); crystallized mirabilite restrains Rhizoma Sparganii (sanleng); Radix Aconiti (chuanwu) and Radix Aconiti Kuznezoffii (caowu) restrain Cornu Rhinoceri (xijiao); Radix ginseng restrains Faeces Trogopterorum (wulingzhi) and Cortex Cinnamomi (guangui) restrains Halloysitum Rubrum (chishizhi). These drugs, when put together, will restrain or neutralize each other’s actions. Modern pharmacological studies on the 18 incompatible medicaments and 19 medicaments of mutual restraint have not yet elucidated the mechanism of these actions. 8.3 Contra-indication during pregnancy Some drugs used during pregnancy may endanger the fetus, causing abortion even miscarriage. Drugs that are prohibited or should be used with great caution during pregnancy are those that have a drastic action or are very toxic, such as Semen Crotonis (badou), Hirudo (leech, shuizhi), Tabanus (gadfly, mengchong), Radix Euphorbiae Pekiensis (daji), Flos Genkwa (yuanhua), musk, Rhizoma Sparganii (sanleng), Rhizoma Curcumae Zedoariae (ezhu) and mylabris (Chinese blistering beetle, banmao). Drugs that should be used with great caution are those with drastic actions of relieving qi stagnation and removing blood stasis, or are highly pungent, very warm, highly lubricating or purgative, such as Fructus Aurantii Immaturus (zhishi), Semen Aracae (binglang), Semen Persicae (taoren), Radix Aconiti Lateralis Praeparata (fuzi) and Rhizoma Ligustici Chuanxiong. 8.4 Dietetic restraint (food taboo) During treatment with herbal drugs, some types of food that are unsuitable for the condition of the patient or are contra-indicative to some drugs should be avoided or their intake limited. Uncooked or cold food is unsuitable in cases of cold syndrome; and hot, pungent or greasy food is unsuitable in case of warm syndrome. In take of pepper, chillies, alcoholic beverages, garlic, etc. should be limited in cases of dizziness, insomnia and agitation. For patients with indigestion due to deficiency of the spleen and stomach, fried, greasy and sticky foods should be avoided. Patients with suppurative infection on the skin and pruritus should not take fish, shrimp, crab or other seafood or irritating foods. In addition, there are records in the ancient literature that Radix Dichroae (changshan) is incompatible with Bulbus Allii Fistuloi (Chinese green onion, scallion, cong); Radix Rehmanniae and Radix Polygoni Multiflori (heshouwu) are contra-indicated for Chinese green onion, garlic and radish. Peppermint counteracts turtle flesh; Porai is not compatible with vinegar; Corapax Trionycis (turtle shell) is antagonistic to Amaranthus tricolor (xian); honey to scallions, and so on. 8.5 Dosage of drugs Dosage is determined by the following factors: 8.5.1 Properties of drugs In general, drastic and toxic drugs should be given in small doses at the beginning, and the doses should be increased gradually. However, drugs of less-potency or great density (such as mineral and shell drugs) should be given in larger doses. 8.5.2 Compatibility and form of preparation Since there are principal, adjuvant, auxiliary and conductant drugs in a prescription, the dosage of the principal drug(s) is usually larger than that of the others. As to the form of preparation, the dosage of drugs in a decoction is larger than that in bolus or powder forms. 8.5.3 Condition of the disease, and constitution and age of the patient The dosage given in the case of serious, emergency and stubborn conditions should be, in general, larger. For mild and chronic diseases, the dosage may be smaller. Strong patients can take larger doses, while aged or weak persons, children should take smaller doses. The dosage for a child over six years old should be half of that for an adult. The dosage for a child under five should be a quarter of that for an adult, and for an infant even smaller. 8.5.4 Geographic features The temperature in the southern areas of China is high, hence the dosage of diaphoretics (drugs for treating exterior syndromes) should be small. As the temperature in the northern parts of China is lower, the dosage should be larger. In the summer, humidity is high, and so the dosage of drugs with fragrant odors to resolve dampness should be larger, while the dosage of diaphoretics and drugs for warming yang should be smaller. In winter, drugs for warming yang and diaphoretics may be given in larger doses. 9.1 The conventional way of preparing TCD for administering to patients is to decoct or boil the drugs. TCD should be boiled in a vessel with stable chemical properties, such as an earthenware or enamel pot. Clean water is then poured in and over the surface of the drug(s). The drug(s) is then immersed for about 60 minutes, then boiled with high heat and then gentle heat for 20-40 minutes, depending on the property of the drug(s). Later, the supernatant is taken out. Water is poured in again, the drug(s) is boiled once again. Usually two or three supernatants are poured in together, and divided into two portions to be given to patients. 9.2 Some drugs should be decocted first, such as some drugs of mineral and shell origin, namely Gypsum Fibrosum (gypsum, shigao), Concha Ostreae (oyster shell, muli), Concha Haliotidis (sea-ear shell, shijueming), Plastron Testudinis (tortoise plastron, guiban), etc. Because such drugs are firm and hard, their active ingredients are difficult to boil out. They should be boiled 15 minutes before other drugs are boiled. 9.3 Some drugs should be boiled later than other drugs, such as aromatic drugs of which the active ingredients are easy to evaporate or decompose. So, they should be put into the decoction after other drugs have been boiled for 5-15 minutes. Then the decoction is boiled for another five minutes. Such drugs include Herba Menthae (field mint, bohe), Fructus Amomi (spiny amomum fruit, sharen) and Radix et Rhizoma Rhei (rhubarb, dahuang). 9.4 Some drugs should be wrapped before decoction. This is important for drugs that are powdered, downy or mucilaginous, such as Flos Inulae (xuanfuhua), Semen Plantaginis (cheqianzi), etc. 9.5 Some drugs should be decocted separately. This is important for certain valuable drugs which are usually administered in small amounts, such as ginseng, American ginseng, rhinoceros horn, etc. After decoction, the drugs may be administered separately or mixed with other decocted drugs. 9.6 Some drugs should be taken after powdering and pouring water on them and stirring the solution or suspension. This is important for drugs that are not suitable for boiling, such as amber, Radix Notoginseng (sanqi), etc., and for some liquid drugs such as bamboo juice, fresh ginger juice, etc. 9.7 Some drugs should be dissolved in water or melted before being taken. Drugs such as malt extract or ass-hide glue are in this category. (10) Method and Time of Administration of TCD For decoctions, one dose per day is usually enough. The decoction may be divided into two or three portions, to be taken two or three times a day. For serious or acute conditions, a decoction should be taken every four hours until the patient’s condition improves. Tonic drugs should be taken before meals. Patients with cold syndrome should take warm decoctions, and vice versa. If TCD are in pill or tablet form, they can be taken orally with warm water. The dosage will be specified by the physician. In short, the modern science of Chinese materia medica encompasses a series of disciplines, such as pharmacognosy, phytochemistry, pharmacology and formulations of TCD, processing of TCD, pharmaceutics, clinical pharmacology of TCD, etc. Meanwhile, there are still many aspects of TCD which modern technology can shed further light on. (Source: The Essentials of Traditional Chinese Herbal Medicine, Foreign Language Press, 2001) |
| Tools: Save | Print | E-mail | Most Read |
 |
| Related Stories |
