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9. What are the proper dosages when prescribing herbs?

The exact dosage of each herb is usually given in textbooks of Chinese herbal medicine. Nowadays, herb weights are given in metric units (grams or milligrams) instead of in traditional Chinese weights (Liang, Qian and Fen). The dosage of a single herb mentioned in books is always the dosage for 1 day.

The dosages of the herbs in a formula are more complicated and they are not always for 1 day. In addition, the herbs are weighed according to different systems in different dynasties, so it is important to read the preparation of the formula carefully, as well as possess some knowledge of the classic in which the formula was recorded.

Here we discuss only the dosage of single herbs.

To achieve the therapeutic results, it is important not only to choose the proper herbs, but also to use the proper dosage. For a junior practitioner, it is not so easy to remember the dosage of each herb, so it is necessary to find an easy way to memorize them.

Generally speaking, in Chinese texts the common dosage of most crude herbs is about 3–9 grams orally per day, which is divided into two or three portions and used during the course of the day. However, in the West it is generally not practical to prescribe the crude herbs for oral use since it takes too much time every day to prepare the decoction and the smell is not always pleasant.

Concentrated herb powders produced in Taiwan and Hong Kong are thus more commonly used. It should be noted that the strength of the concentrated powder is six times stronger than that of the crude herbs, thus the given dosage of most single powdered herbs is 0.5–1.5 grams per day. According to my own experience, however, the correct dosage is generally somewhat lower, at 0.2–0.5 grams. Although the dosage range of most herbs can be remembered in this way, there are some exceptions. In the exceptions mentioned, the dosage of the herbs should be memorized individually.

Poisonous herbs

Some poisonous herbs can be dangerous for patients if they are overdosed. The dosage of these herbs should be remembered by heart. As the toxic dose varies for each individual, the therapeutic range is small and only experienced doctors must prescribe these herbs.

The commonly used poisonous herbs are Fu Zi (Aconiti radix lateralis preparata), Wu Tou (Aconiti radix), Xi Xin (Asari herba), Ma Huang (Ephedrae herba), Yang Jin Hua (Flos Daturae), Lei Gong Teng (Tripterygii wilfordii caulis), Wu Gong (Scolopendra), Quan Xie (Scorpio), Bai Hua She (Agkistrodon acutus), Mang Chong (Tabanus), Zhe Chong (Eupolyphaga seu opisthoplatia), Não Yang Hua (Rhododendron molle flos), Tian Xian Zi (Hyoscyamus niger semen), Shan Dou Gen (SophoraeSophorae tonkinensis radix), Sheng Ban Xia (Pinelliae rhizoma), Tian Nan Xing (Arisaematis rhizoma), Bai Fu Zi (Typhonii rhizoma praeparatum), Wei Ling Xian (Clematidis radix), Xian Mao (Curculinginis rhizoma), Cang Er Zi (Xanthii fructus), Wu Zhu Yu (Evodiae fructus), Hua Jiao (Zanthoxyli fructus) and Yuan Zhi (Polygalae radix).

Poisonous substances that are used for special pathological situations, but are not often used, are Ku Lian Pi (Meliae cortex), He Shi (Carpesii fructus), Gua Di (Pedicellus cucumeris), Li Lu (Veratri nigri radix et rhizoma), Chang Shan (Dichroae febrifugae radix), Gan Sui (Euphorbiae kansui radix), Da Ji (Knoxiae radix), Yuan Hua (Genkwa flos), Shang Lu (Phytolaccae radix), Qian Niu Zi (Pharbitidis semen), Ba Dou (Crotonis fructus) and Zhu Sha (Cinnabaris).

Minerals

Mineral substances can be used at 30 grams per day in traditional decoctions. These include Shi Gao (Gypsum), Ci Shi (Magnetitum), Long Gu (Mastodi fossilium ossis), Mu Li (Ostrea concha), Zhen Zhu Mu (Concha margaritifera usta), Shi Jue Ming (Haliotidis concha) and Wa Leng Zi (Arcae concha). If the concentrated powder is prescribed, the dosage should be about 1–2 grams.

Light herbs

Herbs that are light in weight should be used in a lower dosage: 0.5–3 grams for crude herbs and 0.1–0.5 grams for concentrated powder, such as Tong Cao (Tetrapanacis medulla), Deng Xin Cao (Junci medulla), Ma Bo (Lasiosphaera) and Chan Tui (Cicadae periostracum).

The dosage of single herbs can be varied within the normal dosage range in the following conditions:

• Bland herbs, which promote urination and leach out Dampness, can be used in relatively large dosage; these include Fu Ling (Poria), Yi Yi Ren (Coicis semen), Che Qian Zi (Plantaginis semen) and Hua Shi (Talcum).

• Tonifying herbs can be used in relatively large dosage; these include Huang Qi (Astragali radix), Shu Di Huang (Rehmanniae radix praeparata), Mai Men Dong (Ophiopogonis radix) and Bai He (Lilii bulbus).

• Aromatic herbs that open the orifices, expel Wind-Heat or Wind-Cold and promote Qi movement should be used in relatively small dosage; these include Bing Pian (Borneol), Su He Xiang (Styrax), Bo He (Menthae herba), Chai Hu (Bupleuri radix), Xin Yi (Magnoliae flos), Bai Zhi (Angelicae dahuricae radix), Mu Xiang (Aucklandiae radix) and Sha Ren (Amomi xanthioidis fructus).

• Herbs that are used alone should be in relatively large dosage, whereas in a formula the dosage should be smaller. For instance, Pu Gong Ying (Taraxaci herba) can be used by itself at 15 grams per day to treat carbuncle, but at only 6 grams in a formula with other herbs for treating carbuncle.

• The dosage should be varied according to the constitution and the age of the patient.

For acute diseases, if the patient is young, or the constitution is quite good, the dosage of the herbs that expel exogenous pathogenic factors should be large. For chronic diseases, or if the patient is old and weak, the dosage of the herbs that expel the pathogenic factors should be smaller. The notifying herbs should be started with a smaller dosage, then the dosage should be increased gradually because their cloying nature may cause indigestion.

• The dosage should be varied during the course of treatment. For acute diseases, or in the active stage of chronic diseases, the dosage should be high. When the situation is under control, the dosage should be reduced. Herbs that open the orifices, or induce sweating, diarrhea or vomiting, are used only once.

Afterwards, the dosage must be adjusted according to the condition of the patient.

There are also herbs that should not be used at a high dosage for more than 4 weeks. These include herbs that disperse the Lung-Qi, disperse Wind, Cold and Dampness, strongly reduce Heat-toxin, drain downward, break up Qi stagnation, remove congealed Blood, remove food stagnation, calm the Mind and subdue the Liver-Yang.

These herbs are usually used to treat asthma, rheumatic or rheumatoid arthritis, acute infections, tumors, emotional disturbance, insomnia or hot flushes and night sweats in menopause. In chronic disease, after intensive treatment for 1–4 weeks, these herbs should be used in a lower dosage to keep the condition stable; meanwhile, herbs that tonify or harmonize the functions of internal organs should be used if necessary. The intensive treatment can be repeated according to the disease and the condition of the patient.

Some gentle tonifying herbs can be used for months or even years in low dosage for the purpose of keeping the condition stable, strengthening the body resistance or maintaining good health. In this case, if the treatment course is long, it is better to have breaks. The best time for the break is summer because Summer-Heat or Damp-Heat may weaken the function of the Spleen and the herbs may place extra burden on the Spleen and cause digestive problems.

• The dosage should also be varied according to season and climate. In summer or in tropical countries, herbs that expel Wind and Cold and disperse the Lung-Qi should not be used in high dosage because the pores are not tightly closed.

However, in winter or extremely northerly latitudes, herbs that expel Wind, Cold and Dampness and induce sweating should be used in high dosage.

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