古之方剂，锱铢分两，与今不同。谓如 咀者，即今锉如麻豆大是也。云一升者，即今
之大白盏也。云铢者，六铢为一分，即二钱半也；二十四铢为一两也；云三两者，即今之一
两；云二两，即今之六钱半也。料例大者，只合三分之一足矣。
帝曰∶方制君臣何谓也？岐伯曰∶主病之谓君，佐君之谓臣，应臣之谓使，非上中下三
品之谓也。帝曰∶三品何谓？曰∶所以明善恶之殊贯也。
凡药之所用者，皆以气味为主。补泻在味，随时换气。主病者为君，假令治风者，防风
为君；治上焦热，黄芩为君；治中焦热，黄连为君；治湿，防己为君；治寒，附子之类为君
。兼见何证，以佐使药分治之。此制方之要也。《本草》说，上品药为君，各从其宜也。
《气交变论》云∶夫五运之政，犹权衡也。高者抑之，下者举之，化者应之，变者复
之。此生长化成收藏之理，气之常也。失常则天地四塞矣。失常之理，则天地四时之气，无
所营运。故动必有静，胜必有复，乃天地阴阳之道也。假令，高者抑之，非高者固当抑也，
以其本下，而失之太高，故抑之而使下。若本高，何抑之有？假令下者举之，非下者固当举
之也，以其本高，而失之太下，
故举而使之高。若本下，何举之有？
如仲景治表虚，制桂枝汤方∶桂枝，味辛热，发散，助阳，体轻，本乎天者亲上，故桂
枝为君，芍药、甘草为佐。阳脉涩、阴脉弦，法当腹中急痛，制小建中汤方∶芍药，味酸寒
，主收，补中，本乎地者亲下，故芍药为君，桂、甘草佐之。一则治表虚，一则治里虚，各
言其主用也。后之用古方者，触类而长之，不致差误矣。
古代的方剂，其剂量单位（锱、铢、分、两）与现在不同。所谓“咀”，就是现在将药材锉碎成麻子或豆子大小的颗粒。所说的“一升”，相当于现在的大白瓷盏。所说的“铢”，六铢等于一分，即二钱半；二十四铢等于一两；所说的“三两”，相当于现在的一两；所说的“二两”，相当于现在的六钱半。按照这种折算比例，较大的剂量只需取原方的三分之一即可。
黄帝问：方剂的君臣配伍原则是什么？岐伯回答：主治疾病的药物称为君药，辅助君药治疗的称为臣药，配合臣药发挥作用的称为使药，这并不是指《神农本草经》中上、中、下三品的分类。黄帝问：那三品是指什么？岐伯说：是用来明确药物性质善恶差异的。
凡是药物的使用，都以气味为主要依据。补益或泻实的作用取决于药味，而随季节变化则需调整药气。主治疾病的药物为君药，例如治疗风病，以防风为君药；治疗上焦热证，以黄芩为君药；治疗中焦热证，以黄连为君药；治疗湿邪，以防己为君药；治疗寒证，以附子等药物为君药。如果兼有其他证候，则由佐药和使药分别进行治疗。这是制方的关键所在。《本草》中说，上品药作为君药，各自根据适宜的情况而定。
《素问·气交变大论》说：五运的政令，就像秤杆和秤砣一样平衡。高的要压制它，低的支持起它，化生者顺应它，变异者复归它。这是生长、化育、收敛、收藏的道理，是气的正常规律。如果失去常态，天地之气就会闭塞不通。失去常态的道理在于，天地四时的气无法正常运行。所以动必有静，胜必有复，这是天地阴阳运行的法则。举例来说，“高者抑之”，并不是说高的本来就应当压制，而是因为它本应低下却过高了，所以要压制它使其降低。如果本来就已经很高，为什么要压制呢？举例来说，“下者举之”，并不是说低的本来就应当支持，而是因为它本应高却过低了，所以要支持它使其升高。如果本来就已经很低，为什么要支持呢？
例如张仲景治疗表虚证，制定桂枝汤方：桂枝，味道辛热，具有发散作用，能助阳，质地轻扬，属于天之气而亲上，所以桂枝为君药，芍药、甘草为佐药。如果出现阳脉涩、阴脉弦的脉象，按照法度应当出现腹中急痛的症状，于是制定小建中汤方：芍药，味道酸寒，主收敛，能补中焦，属于地之气而亲下，所以芍药为君药，桂枝、甘草为佐药。一个方子治疗表虚，一个方子治疗里虚，各自说明其主要用途。后世使用古方的人，能够触类旁通、灵活变通，就不会出现差错错误了。
Ancient prescriptions used weight units (zi, zhu, fen, liang) different from those of today. The term "ju" (chewing/crushing) refers to crushing herbs into pieces the size of hemp seeds or beans today. One "sheng" (a unit of volume) is equivalent to a large white porcelain cup today. Six "zhu" equal one "fen," which is two and a half qian; twenty-four "zhu" equal one "liang"; three "liang" in ancient times equals one "liang" today; two "liang" in ancient times equals six and a half qian today. According to this conversion ratio, for larger dosages, taking only one-third of the original amount is sufficient.
The Yellow Emperor asked: What is meant by the Jun-Chen-Zuo-Shi (Sovereign-Minister-Assistant-Courier) structure of prescriptions? Qibo replied: The herb that treats the main disease is called the Sovereign (Jun); the herb that assists the Sovereign is called the Minister (Chen); the herb that responds to and coordinates with the Minister is called the Courier (Shi). This does not refer to the classification of Superior, Middle, and Inferior grades found in materia medica. The Yellow Emperor asked: What do these three grades mean? Qibo said: They are used to clarify the differences between beneficial and harmful properties.
In the use of all herbs, aroma and flavor are primary. Tonification or purgation depends on flavor, while adjustment according to seasons involves changing qi properties. The herb treating the main disease serves as the Sovereign. For example, to treat wind disorders, Fangfeng (Saposhnikovia Root) is the Sovereign; to treat heat in the Upper Jiao, Huangqin (Scutellaria Root) is the Sovereign; to treat heat in the Middle Jiao, Huanglian (Coptis Rhizome) is the Sovereign; to treat dampness, Fangji (Stephania Root) is the Sovereign; to treat cold, Fuzi (Aconite Lateral Root) and similar herbs are the Sovereign. If other syndromes are present, Assistant and Courier herbs are used to address them separately. This is the essence of prescription formulation. The Bencao (Materia Medica) states that Superior grade herbs serve as Sovereigns, chosen according to appropriateness.
The Qi Jiao Bian Lun (Treatise on Changes in Qi Interaction) states: The administration of the Five Movements is like a balance scale. What is high is suppressed; what is low is raised; what transforms is responded to; what changes is restored. This is the principle of growth, transformation, harvest, and storage, the normal law of Qi. When this norm is lost, the Qi of heaven and earth becomes blocked. The reason for losing the norm is that the Qi of heaven, earth, and the four seasons cannot circulate properly. Therefore, movement must be followed by stillness, and dominance must be followed by restoration; this is the Way of Yin and Yang in heaven and earth. For instance, "suppressing the high" does not mean that what is high should inherently be suppressed, but rather that because it was originally low but became excessively high, it is suppressed to lower it. If it were originally high, why suppress it? Similarly, "raising the low" does not mean that what is low should inherently be raised, but because it was originally high but became excessively low, it is raised to elevate it. If it were originally low, why raise it?
For example, Zhang Zhongjing treated Exterior Deficiency with the Guizhi Tang (Cinnamon Twig Decoction): Guizhi (Cinnamon Twig), with its pungent and hot flavor, has dispersing properties and aids Yang; being light in nature, it follows Heaven's Qi and tends upward, so Guizhi is the Sovereign, while Shaoyao (Peony Root) and Gancao (Licorice Root) are Assistants. If the Yang pulse is choppy and the Yin pulse is taut, the method dictates abdominal acute pain, leading to the formulation of Xiaojianzhong Tang (Minor Construct the Middle Decoction): Shaoyao (Peony Root), with its sour and cold flavor, governs astringency and tonifies the Middle; being heavy in nature, it follows Earth's Qi and tends downward, so Shaoyao is the Sovereign, while Guizhi (Cinnamon Twig) and Gancao (Licorice Root) are Assistants. One formula treats Exterior Deficiency, the other treats Interior Deficiency, each explaining its primary function. Those who use ancient formulas in later generations, applying these principles flexibly and extending them by analogy, will avoid errors.