The formation and development of prescriptions have undergone a very long historical period. As far back as in the early period of slavery society, man began to use a single drug to prevent and treat diseases. In the Shang dynasty, because of the increased variety of drugs and the enrichment of knowledge about diseases, more drugs were selected according to the different symptoms of illness to formulate compound prescriptions for clinical uses. People began to use compound drugs instead of a single one, thus greatly improving the curative effect. This is the embryonic form of prescriptions of TCM. A prescription book entitled "The Prescriptions for Fifty-tow Kinds of Disease" was unearthed in 1979 from the No.3 Han Tomb at Ma Wang Dui, Changsha, Hunan Province. It is the earliest extant medical formulary in China.

With the development of traditional Chinese medicine, the prescription itself has also become perfected and enriched. Around the Warring States period and in the Qin and Han Dynasties, a classical writing of TCM entitled "The Yellow Emperor" , "Canon of Internal Medicine" came out. This is the earliest book dealing with the basic theories of the science of TCM formulae, such as the principle of formulating a prescription, incompatibility of drugs in a prescription, some dosage forms and their usages. The book consisting of 13 prescriptions has laid a solid foundation for the formation and the development of the science of TCM formulae.

Zhang Zhongjing, an outstanding physician in the Eastern Han Dynasty after diligently seeking the ancient experience and book knowledge and extensively collecting numerous prescriptions, compiled "Treatise on Febrile and Miscellaneous Diseases" which contains 269 prescriptions. This book gives interpretations in detail to the modification of the prescriptions and their administrations. The dosage forms are also quite excellent. Therefore, the book has been honored as the "forerunner of prescription books" by all the later physicians.

In the prosperous period of the Tang Dynasty, more voluminous prescription writings came out one after another and promoted the development of science of TCM formulae, such as "The prescriptions Worth a Thousand Gold for Emergencies" and "A Supplement to Essential Prescriptions Worth a Thousand Gold for Emergencies" , compiled by Sun Simiao, and "The Medical Secrets of an Official" compiled by Wang Tao consisting of more than six thousand prescriptions. The three medical formularies representing the major achievements made before the Tang Dynasty collected famous earlier prescriptions in the previous historical periods and some foreign prescriptions used in the Tang Dynasty and preserved the materials on prescriptions.

In the Song Dynasty, the government once organized outstanding physicians to compile "Peaceful Holy Benevolent Prescriptions" (with 16834 prescriptions), "General collection for Holy Relief" (with approximately 20000 prescriptions), and "Prescription of Peaceful Benevolent Dispensary" (with 788 prescriptions). The last one was compiled on the bases of the revision and supplement to formularies collected by the Official Pharmaceutic Bureau. It is one of the earliest formulary in the world compiled by the National Pharmaceutic Bureau. Each prescription gives interpretations in detail to its indications, ingredients and preparation of drugs. This prescription book a "legal" formulary of Chinese patent medicines in the Song Dynasty and also the first pharmacopoeia of the Chinese patent medicines is a big step towards the standardization of prescription.

"Expounding on the Treatise on Febrile Diseases" compiled by Cheng Wuji, a physician I the Jin Dynasty, selected 20 prescriptions from the book " Treatise on Febrile Disease" and analysed them in detail, especially clearly described the different roles of the principal, assistant, adjuvant and guiding drugs. It is the first theoretical book on the interpretations of prescriptions and contributes a great deal to the development of theoretical prescription treatises of later periods. Dr. Zhu Su of the Ming dynasty and others collected almost all the medical formularies having been used before the fifteenth century and compiled the most voluminous medical book "Prescriptions for Universal Relief" with as many as 61739 prescriptions in it.

In the Qing dynasty, with the emergence and development of the schools of epidemic febrile diseases, numerous famous prescriptions for epidemic febrile diseases came into being, enrich and perfecting the contents of pharmacology of TCM formulae. In addition, in the Ming and Qing Dynasties a lot of monographs on prescriptions were published such as "Textual Criticism on Prescriptions" and "Collection of Prescriptions with Notes", thus further promoting the development of the theoretical research of the science of TCM formulae.

Since the founding of the People's Republic of China, a great number of prescription book have come out. Many ancient prescriptions, secret prescriptions, proved prescriptions have been collected, systematized, researched and widely applied to deferent clinical departments; their therapeutic mechanism and compatible properties have been explored by experimental researches. Meanwhile a lot of new effective prescriptions have been created and the reformation in the dosage forms of prescriptions have been carried out. As a result, a new prospect in the development of science of TCM formulae has been opened up.

The formation of a prescription is neither simply to pile up drugs with similar functions and effects nor "to treat the head when the head aches and to treat the foot when the foot hurts", that is to say, only to treat the symptoms but not the syndrome (zheng) in TCM or the disease. It is on the basis of the differentiation of syndromes and establishment of the therapeutic methods, to pick out proper drugs and organically constitute them in the light of the principles of forming a prescription.

By the principle of forming a prescription is mainly meant the compatible theory of principal, assistant, adjuvant, and guiding drugs in the prescription of TCM. To form a prescription in accordance with this theory, it is necessary to make a clear distinction between the principal drug and the secondary ones and make them supplement and restrict one another, thereby, producing the most effective result in the treatment of diseases.

Principal drug: A principal drug is one which is aimed at producing the leading effects in treating the cause or the main symptom of a disease. It holds sway in the whole prescription.

Assistant drug: An assistant drug is firstly meant the drug which help strengthen the effect of the principal drug and is secondly meant the drug which is aimed at producing the leading effect in the treatment of the accompanying symptoms.

Adjuvant drug: An adjuvant drug can be divided into three types, the first type assists the principal and assistant drugs to strengthen their therapeutic effects or treats less important symptoms by itself; the second reduces or clears away the toxicity of the principal and assistant drugs so as to prevent the toxic effect and side effect of the drugs from coming into existence; the third, aimed at dealing with possible vomiting in serious cases after taking decoction with too potent effect, possesses the properties opposite to those of the principal drug in compatibility, but produces supplementing effects in the treatment of diseases.

Guiding drug: A guiding drug can be subdivided into two types: one is known as the medicinal guide leading the other drugs in the prescription to the affected site; the second is known as a mediating drug coordinating the effects of various ingredients in the prescription.

As mentioned above, a principal ingredient should be used as the dominator in a prescription, with an assistant, adjuvant and guiding drugs subordinate to it and the four kinds of drugs supplementing one another and playing the curative roles together.

----------- Source Prescriptions of Traditional Chinese Medicine