Dosage
The amount of medicinal herbs to be taken is called dosage, which signifies the daily amount of one particular herb by adults, and secondly shows the comparative measurements of medicinal herbs in the same prescription and is also known as relative dosage. Generally speaking, the amount following each herb refers to the daily amount of one dried raw herb by adults in making decoction or the daily amount of powder by adults, which is ground from dry raw herbs. As to the amount of Chinese medicinal herbs to be taken, we mostly take weight as the unit of measurement, and take quantity and capacity as the unit for the special ones. Now we take the metric system (g) as the unit of measurement, which is now stipulated in the mainland of China.
As the dosage of a medicinal herb has direct relationship with its therapeutic effect, a medicinal herb when used below its level of effective dosage, will not achieve desired results£» the dose of a certain herb when used beyond its limit, may often damage the healthy qi and is also wasted. Since most Chinese medicinal herbs are generally crude plants with fairly moderate nature and a wide-safety range of dosage, their doses may not be used so strictly as those of chemicals. But some of them are also drastic or extremely poisonous, so their doses must be used properly to get the best therapeutic effects and meanwhile prevent patients from poisoning.
The dosage of Chinese medicinal herbs is yet affected by the following factors, and it is used flexibly.
5.1.1 Properties of medicinal herbs
The medicinal herbs moderate in nature can be used in a large amount; those drastic or poisonous in nature must be used in a small amount; those light in property should be used in a small amount; those heavy in property, such as mineral and shell but without toxin can be used in a large amount; fresh plant medicinal herbs, since they contain water, should be used in amount about twice as much as dry ones.
5.1.2 Compatibility and dosage
The amount of a singly used herb is usually large than that applied in a prescription; the amount of a main ingredient in a prescription larger than that of an accessory one; the amount of a medicinal herb in making decoction larger than that in pills or powder. For instance, Rougui (Cortex Cinnamomi) used in decoction usually weights 3 g, but if used in pill or powder, it is only needed 0.5 lg.
5.1.3 The condition of illness, the patients' physique and age
The amount of a medicinal herb used in the treatment of serious and acute disease must be fairly larger while the amount used in the treatment of the mild or chronic comparatively smaller. The amount used for those with strong physique must be larger while for those with weak physique, the old and children, the dose generally smaller. For children over 6 years, half the dose of an adult's is used; for the children below 5 years, 1/3 - 1/2 dose of an adult's is used; for an infant, the dose should be much smaller.
Besides, the dose of expensive medicines under ensurance of medicinal effects should be small, such as, Shexiang ( Moschus Artifactus ), Niuhuang ( Calculus Bovis)£» etc., that we should avoid waste of medicinal materials and economic burden on the patient£» the dose must be used flexibly according to the differences of patient's physique and areas, climates, and seasons, etc.
