The art of prescriptions, also known as recipes o ffomulas, in traditional Chinese herbal medicine has undergone significant change through centuries. Like other aspects of TCM, it is important to understand the nature of this development in order to claerly appreciate how the prescriptions came to be, and how to use them in clinic to the best effect.
The prescriptions in TCM are not merely collections of medicinal substances in which the actions of one herb are simply added to those of another in a cumulative fashion. They are complex recipes of interrelated substances, each of which affects the actions of the others in the prescriptions. It is this complex interaction which makes the prescriptions so effective, but also difficult to study.
Every medicinal substance has its strength and shortcomings. An effective prescription is one in which the substance are carefully balanced to accentuate the strength and reduce the side-effects. The combination of substances in a prescription creates a new therapeutic agent that can treat diseases much more effectively than a single substance.
Constructing an effective prescription involves more than simply putting ingredients together to obtain a certain effect. One needs a principle to guide the construction so that the ingredients are combined in an optional fashion. The orderly arrangement of ingredients in a prescription is called a hierarchy. Traditional Chinese society was always very conscious of rank, which revolved in the first instance around the emperor and his court. For this reason, the terms used to signify the importance or rank of the ingredients in s prescription reflect those used at court. The four ranks of ingredients in the hierarchy of a prescription are the jun(usually translate into monarch, king, principal or chief), chen(usually translate into minister, adjutant, associate or deputy), zuo (usually translate into assistant or adjustant) and shi (usually translate into guide, messenger, conductant or envoy).
Not all prescriptions contains the full hierarchy of ingredients. In fact, it would be quite unusual for a prescription to include all the types of minister-ingredients, assistant-ingredient and guide- ingredients. If the monarch-ingredients and minister-ingredients are not toxic, there is no need for corrective assistant-ingredients. Sometimes the monarch-ingredient focuses on the location of the disorder, obviating the need for a guide-ingredient.