大泻血分湿热，下有形积滞
大苦大寒。入足太阴（脾），手足阳明、厥阴（大肠、胃、心包、肝）血分。其性浮而
不沉，其用走而不守。若酒浸，亦能引至高之分（仲景太阳门调胃承气汤，大黄注曰酒浸；
阳明门大承气汤，大黄注曰酒洗；少阳阳明小承气汤，大黄不用酒制，皆有分别。东垣曰∶
邪气在上，非酒不至。若用生者，则遗至高之邪热。病愈后，或目赤、喉痹、头痛、膈上热
疾生也）。用以荡涤肠胃，下燥结而除瘀热。
治伤寒时疾，发热谵语（大肠有燥粪，故谵语，宜下之。谵，音占），温热瘴疟，下痢
赤白，腹痛里急，黄胆水肿，症瘕积聚（积久成形谓之积，属阴；聚散无常谓之聚，属阳。
积多是血或食或痰，聚多是气），留饮宿食，心腹痞满，二便不通（皆土郁，夺之），吐血衄
血，血闭血枯，损伤积血，一切实热，血中伏火。行水除痰，蚀脓消肿，能推陈致新。然伤
元气而耗阴血（下多亡阴），若病在气分，胃虚、血弱人禁用（病在气分而用之，是为诛伐
无过。东垣曰∶能推陈致新，如定祸乱以致太平，所以有将军之号。时珍曰∶仲景泻心汤，
治心气不足吐衄血者，用大黄。黄连、黄芩，乃泻心包、肝、脾、胃四经血中之伏火也。又
治心下痞满按之软者，用大黄、黄连泻心汤，亦泻脾胃之湿热，非泻心也。病发于阴，而反
下之，则痞满。乃寒伤营血，邪结上焦，胃之上脘当心，故曰泻心。经曰∶太阴所至，为痞
满。又曰∶浊气在上，则生 胀是已。病发于阳，而反下之，则结胸。乃热邪陷入血分，亦
在上脘，故大陷胸汤、丸皆用大黄，亦泻脾胃血分之邪，而降其浊气也。若结胸在气分，只
用小陷胸汤；痞满在气分，只用半夏泻心汤。或问心气不足而吐衄，何以不补心而反泻心？
丹溪曰∶少阴不足，亢阳无辅，致阴血妄行，故用大黄泻其亢甚之火。又心本不足，肝、肺
各受火邪而病作，故用黄芩救肺、黄连救肝。肺者阴之主，肝者心之母，血之合也，肺、肝
火退，则血归经而自安矣。寇宗 曰∶以苦泄其热，就以苦补其心，盖一举而两得之。李士
材曰∶古人用大黄治虚劳吐衄，意甚深微。盖浊阴不降，则清阳不生，瘀血不去，则新血不
生也）。
川产锦纹者良。有酒浸、酒蒸、生、熟之不同。生用更峻。黄芩为使（欲取通利者，不
得骤进谷食，大黄得谷食，便不能通利耳。《夷坚志》∶汤，火伤者，捣生大黄，醋调敷，
止痛无瘢）。
大黄味极苦、性极寒。归入足太阴脾经，以及手阳明大肠、足阳明胃、手厥阴心包、足厥阴肝的血分。它的药性轻浮而不沉降，作用趋向是通行而不停留。如果用酒浸泡，也能引导药力到达身体上部（张仲景在《伤寒论》太阳病篇的调胃承气汤中，注明大黄用酒浸；阳明病篇的大承气汤中，注明大黄用酒洗；少阳阳明并病的小承气汤中，大黄不用酒制，这些用法都有区别。李东垣说：邪气在上部，不用酒引路药物就达不到。如果直接用生大黄，就会遗漏上部的邪热。病愈后，可能会出现眼睛发红、咽喉肿痛、头痛、胸膈以上热性疾病等后遗症）。因此用它来荡涤肠胃，攻下燥结，清除瘀热。
治疗伤寒及时行疫病引起的发热、胡言乱语（因为大肠有干燥粪便，所以出现谵语，适宜用泻下法。谵，读音为zhān）、温热性质的瘴疟、痢疾拉出红白黏液、腹痛且肛门急迫、黄疸、水肿、症瘕积聚（积久成形称为“积”，属于阴证；聚散无常称为“聚”，属于阳证。积多由血、食或痰引起，聚多由气引起）、水饮停留、宿食停滞、心腹部痞塞胀满、大小便不通（这些都是土气郁结，需要用夺法疏通）、吐血、鼻出血、经闭、血枯、外伤导致的积血、一切实热证、血中潜伏的火邪。它能行水利尿、祛除痰浊、腐蚀脓液、消肿，能够推陈出新。但是它会损伤元气、耗伤阴血（泻下过多会导致亡阴），如果病在气分，或者胃虚、血弱的人禁用（如果在气分病中使用它，就是诛伐没有过错的部位。李东垣说：大黄能推陈致新，就像平定祸乱以达成太平，所以它有“将军”的称号。李时珍说：张仲景的泻心汤，治疗心气不足导致的吐血、衄血，使用大黄、黄连、黄芩，这是为了清泻心包、肝、脾、胃四经血中的伏火。又治疗心下部痞满、按之柔软的病症，使用大黄黄连泻心汤，这也是清泻脾胃的湿热，并非真正泻心。病发于阴证，反而误用泻下法，就会导致痞满。这是因为寒邪伤了营血，邪气结聚在上焦，胃的上脘正当心脏位置，所以叫作“泻心”。《内经》说：太阴经受邪所致，会出现痞满。又说：浊气停留在上部，就会产生胀满，说的就是这个道理。病发于阳证，反而误用泻下法，就会导致结胸。这是因为热邪陷入血分，也位于上脘，所以大陷胸汤、丸都使用大黄，这也是清泻脾胃血分的邪气，并降下浊气。如果结胸在气分，只用小陷胸汤；痞满在气分，只用半夏泻心汤。有人问：心气不足导致吐血、衄血，为什么不补心反而泻心？朱丹溪说：少阴不足，亢盛的阳气失去辅助，导致阴血妄行，所以用大黄泻去亢盛过甚的火邪。另外心本身不足，肝、肺各自受到火邪侵袭而发病，所以用黄芩救肺、黄连救肝。肺是阴的主宰，肝是心的母亲，也是血的合脏，肺、肝的火退去，血液就能回归经脉而自然安宁。寇宗奭说：用苦味泄除热邪，也就是用苦味补心，这是一举两得。李士材说：古人用大黄治疗虚劳导致的吐血、衄血，用意非常深微。因为浊阴不下降，清阳就不能上升；瘀血不去除，新血就不能生成）。
四川出产的带有锦纹的大黄品质优良。有大黄经过酒浸、酒蒸、生用、熟用的不同区别。生用效力更猛烈。黄芩作为使药（想要取得通利的效果，不能突然进食谷物，大黄得到谷物帮助，才能发挥通利的作用。《夷坚志》记载：对于汤火烫伤者，捣碎生大黄，用醋调和敷贴，止痛且不留疤痕）。
Dahuang (Rhei Radix et Rhizoma) strongly clears damp-heat from the Blood level and purges有形 (solid) accumulations and stagnation within.
It is extremely bitter and extremely cold. It enters the Foot-Taiyin Spleen channel, as well as the Hand-Yangming Large Intestine, Foot-Yangming Stomach, Hand-Jueyin Pericardium, and Foot-Jueyin Liver blood levels. Its nature is floating but not sinking; its action is moving but not stationary. If soaked in wine, it can also guide medicinal power to the upper parts of the body (Zhang Zhongjing, in the Taiyang chapter of *Shanghan Lun* for Tiaowei Chengqi Tang, notes Dahuang should be soaked in wine; in the Yangming chapter for Dachengqi Tang, notes Dahuang should be washed with wine; in the Shaoyang-Yangming combined disease Xiaochengqi Tang, Dahuang is not processed with wine; these usages have distinct differences. Li Dongyuan said: Pathogenic factors in the upper part cannot reach their target without wine as a guide. If raw Dahuang is used, the pathogenic heat in the highest parts will be neglected. After recovery, symptoms such as red eyes, throat obstruction, headache, or heat diseases above the diaphragm may arise). Therefore, it is used to scour the intestines and stomach, purge dryness and accumulation, and remove stasis and heat.
It treats febrile diseases and epidemic diseases caused by Shanghan (Cold Damage), characterized by fever and delirious speech (delirious speech occurs due to dry feces in the Large Intestine, so purgation is indicated. "Zhan" is pronounced zhān); warm-heat type malarial fevers (Zhangnuo); dysentery with red and white discharge; abdominal pain with tenesmus; jaundice and edema; masses and accumulations (long-standing formations are called "Ji" [accumulation], belonging to Yin; those that gather and scatter irregularly are called "Ju" [aggregation], belonging to Yang. Ji often involves blood, food, or phlegm; Ju often involves Qi); retained fluids and old food retention; epigastric and abdominal fullness and stuffiness; blockage of both urination and defecation (all represent stagnation of Earth, requiring the "duo" method to drain them); hematemesis (vomiting blood) and epistaxis (nosebleed); amenorrhea and blood exhaustion; traumatic blood stasis; all types of excess heat; and latent fire within the blood. It promotes water metabolism, eliminates phlegm, erodes pus, reduces swelling, and can push out the old to bring forth the new. However, it damages Yuan Qi (Original Qi) and consumes Yin blood (excessive purgation leads to loss of Yin). It is strictly contraindicated if the disease is at the Qi level, or in patients with deficient Stomach Qi or weak blood (using it when the disease is at the Qi level constitutes punishing the innocent. Li Dongyuan said: Dahuang pushes out the old and brings forth the new, much like quelling chaos to establish peace, hence its title "General". Li Shizhen said: Zhang Zhongjing's Xiexin Tang treats vomiting and nosebleeding due to insufficient Heart Qi by using Dahuang, Huanglian (Coptidis Rhizoma), and Huangqin (Scutellariae Radix); this clears latent fire in the blood of the Pericardium, Liver, Spleen, and Stomach channels. It also treats epigastric fullness that is soft upon pressure using Dahuang Huanglian Xiexin Tang, which clears damp-heat in the Spleen and Stomach, rather than truly draining the Heart. When a disease originates from a Yin pattern and is mistakenly treated with purgation, epigastric fullness results. This is because cold has injured the Ying (Nutrient) blood, and pathogens are knotted in the Upper Jiao. The upper part of the Stomach corresponds to the heart region, hence it is called "draining the Heart". The Classics state: What arrives via the Taiyin manifests as fullness. Also: Turbid Qi remaining in the upper part generates distension. This is exactly what is meant. When a disease originates from a Yang pattern and is mistakenly treated with purgation, chest binding (Jie Xiong) results. This is because heat pathogens have sunk into the Blood level, also located in the upper epigastrium; thus, Da Xianxiong Tang and Wan both use Dahuang to clear pathogens in the Spleen and Stomach blood level and descend turbid Qi. If chest binding is at the Qi level, only Xiao Xianxiong Tang is used; if fullness is at the Qi level, only Banxia Xiexin Tang is used. One might ask: Why drain the Heart instead of tonifying it when there is insufficient Heart Qi causing bleeding? Zhu Danxi said: Insufficiency of Shaoyin leads to hyperactive Yang lacking support, causing wild movement of Yin blood; thus, Dahuang is used to drain the excessively hyperactive fire. Furthermore, the Heart itself is insufficient, while the Liver and Lung are afflicted by Fire pathogens; therefore, Huangqin is used to rescue the Lung, and Huanglian to rescue the Liver. The Lung is the master of Yin, and the Liver is the mother of the Heart and the confluence of blood. When the Fire of the Lung and Liver subsides, blood returns to its vessels and calms naturally. Kou Zongshi said: Using bitterness to drain heat is simultaneously using bitterness to tonify the Heart, achieving two goals with one move. Li Shicai said: The ancients' use of Dahuang to treat vomiting and nosebleeding from consumptive diseases was profound. Because if turbid Yin does not descend, clear Yang cannot ascend; if stasis is not removed, new blood cannot be generated).
Dahuang produced in Sichuan with brocade-like patterns is of superior quality. There are differences in processing: wine-soaked, wine-steamed, raw, and cooked. Raw usage is more potent. Huangqin (Scutellariae Radix) serves as an assistant herb (to achieve unblocking and promoting effects, one must not suddenly consume grains; Dahuang requires grain assistance to exert its unblocking effect. *Yijian Zhi* records: For scalds and burns, crush raw Dahuang, mix with vinegar, apply externally; it stops pain and leaves no scar).