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(Zhang Zhongjing)
Treats the condition where early purgation in Cold Damage (Shanghan) leads to chest fullness without pain, termed Pi syndrome (Pih), accompanied by chills and vomiting, with inability to ingest food. This is not Chaihu Tang syndrome (Classics state: In Cold Damage after five or six days, if hematemesis and fever occur, indicating Chaihu Tang syndrome, but other purgatives are mistakenly used; if Chaihu symptoms persist, Chaihu Tang may be administered again; although purgation has been performed here, it is not a counter-indication, the patient will inevitably experience shivering and trembling, followed by fever and sweating for resolution. If the epigastrium is full, hard, and painful, this is Jie Xiong syndrome (Chest Binding), treated with Da Xian Xiong Tang; if full but not painful, this is Pi syndrome, Chaihu Tang is contraindicated, and Banxia Xiexin Tang is appropriate. All uses of Xiexin Tang belong to conditions caused by erroneous purgation, not heat pathogens transmitted through meridians.)

Banxia (Pinelliae Rhizoma) (half sheng) Huanglian (Coptidis Rhizoma) (one liang) Huangqin (Scutellariae Radix) Gancao (Glycyrrhizae Radix et Rhizoma, prepared) Renshen (Ginseng Radix) Ganjiang (Zingiberis Rhizoma) (three liang) Dazao (Jujubae Fructus) (twelve pieces).

This formula acts on the Hand-Shaoyin Heart Meridian and Foot-Taiyin Spleen Meridian. Cheng Wuji stated: "Pi" refers to obstruction without smooth flow. Bitter flavor enters the Heart first; to drain the Heart, bitter herbs must be used, hence Huanglian serves as the Sovereign herb.

(After erroneous purgation, Spleen Qi must be deficient), thus dissipating the Pi-heat and resolving via profuse sweating (Old commentary notes: The ingredients of this formula are derived from Lizhong Tang and Renshen Huangqin Tang. Wang Haicang said: When external signs resemble excess conditions requiring purgation, but the pulse is fine and weak, precluding purgation, Xiexin Tang is indicated; if the pulse is forceful, Huanglian Xiexin Tang is used; if the pulse is weak, Banxia Xiexin Tang is used. Yu Jiayan said: Various Xiexin Tangs originally aim to clear fluid retention; since this case involves vomiting, Banxia is elevated to Sovereign status. Cheng Jiaoqian said: Although Pi syndrome involves deficiency pathogens, when exterior qi sinks into the interior and stagnates in the distribution of Heart Yang, cold transforms into heat. Once cold has transformed into heat, it cannot disperse outward, yet the heat is not excess, and turbid qi cannot descend downward. Only by using bitter-cold herbs to guide them downward along the pathogen's location, while simultaneously using acrid-hot herbs to warm against the potential ascent of Yin pathogens from the Lower Jiao, can both Yin and Yang be resolved. Without directly attacking Pi, Pi disperses naturally, hence the mutual use of cold and hot herbs. If Yin Pi does not involve Yang stagnation, i.e., stagnation has not yet transformed into heat, but is merely a rejection between upper and lower Yin-Yang sectors, the method of draining the Heart is entirely contraindicated. He further stated: People say excessive sweating causes loss of Yang, but do not know that excessive purgation also causes loss of Yang, specifically the loss of Yang within Yin, hence termed loss of Yin. When Lower Jiao Yang suddenly becomes deficient, Qi must rebel upward, causing Upper Jiao Yang to become excess due to lower deficiency, because Fire Qi fails to descend. Treatment often involves draining the upper and tonifying the lower; when the Heart Monarch is pacified by bitter-cold herbs, it can reverse and guide from Yang into Yin, thus the draining action of Huangqin, Huanglian, and Zhizi becomes tonification; if sweating and purgation follow each other...)

Removing Renshen from this formula and adding Gancao (one liang, totaling four liang with the previous amount) creates Gancao Xiexin Tang (Zhang Zhongjing): Treats Cold Damage or Wind Strike where the physician erroneously purges, leading to diarrhea with undigested food, borborygmus in the abdomen, epigastric hardness and fullness, dry belching, and irritability. If the physician purges again, the Pi worsens. This is not accumulated heat, but rather Stomach deficiency with rebellious hostile Qi causing hardness (Because purgation causes interior deficiency and weak Stomach, damaging Yin Qi internally, Gancao is added to harmonize the middle, benefit Stomach Qi, restore True Yin, and clear deficient heat. Zhen Quan... Cold Damage... Intestine... Movement... Treat... Regarding Yin syndromes, they align with Cold, making symptoms even more apparent; thus it is said that in Yang syndrome diarrhea, mistaken warming leads to jaundice and macules, resulting in death...).

Adding Shengjiang (Zingiberis Rhizoma Recens) four liang to this formula creates Shengjiang Xiexin Tang (Zhang Zhongjing): Treats disharmony in the Stomach after resolution via sweating, epigastric hardness, dry belching with food odor, undigested food in stool, water-fluid retention under the hypochondrium, and borborygmus with diarrhea (Rebellious hostile Qi and latent fluid retention binding at the diaphragm cause hardness; Middle Qi disharmony causes dry belching; Stomach deficiency with flourishing fire and pathogenic heat failing to digest grains causes undigested food; water-fluid retention under the hypochondrium, with Earth deficiency failing to control Water, causes borborygmus and diarrhea, termed Xiere Li [Collateral Heat Diarrhea]. Because sweating damages Stomach Qi and externally injures Yang, Shengjiang is added to disperse pathogens, clear fluids, benefit Stomach, and restore Yang. Liu Hejian said: Diarrhea with discoloration of water and food indicates Heat; unchanged color and clear, cold appearance indicate Cold. If the anus is dry and astringent, and urine is yellow and red, even if food remains unchanged, it is still Heat, due to the rapid nature of Fire, where food exits immediately without digestion, termed pathogenic heat failing to "kill" grains). Removing Huangqin and Dazao from this formula, and adding Zhishi (Aurantii Fructus Immaturus), Houpo (Magnoliae Officinalis Cortex), Maiya (Hordei Fructus Germinatus), Baizhu (Atractylodis Macrocephalae Rhizoma), and Fuling (Poria), processed into pills with steamed dough paste, creates Zhishi Xiaopi Wan (Li Dongyuan).