水蛭（熬）二十个 □虫（熬，去翅、足）二十个 桃核（去皮、尖）二十五个 大
黄三两
右四味，捣筛为四丸，以水一升，煮一丸，取七合，服之。晬时当下血，若不下者更
服。
【集解】
柯琴曰：膀胱为府，血本无所容蓄者也。少腹者，膀胱之室也。热结□满，当小便不
利，而反利者，是病不在膀胱之内，而在少腹之内也。其随经之荣血，因瘀热结于少
腹之里，而非膀胱之里也。所以小便虽利，而□满急结如故，是蓄血瘀于少腹也。热
淫于内，神魂不安，故发狂；血瘀不行，则荣不运，故脉微而沉；荣不运则气不宣，
故脉沉而结也。荣气不周于身，则身黄。消谷善饥者，胃火炽盛也；大便反易者，血
之濡也；色黑者，蓄血之化也；善忘者，血不荣智不明也，此皆瘀血之征，非至峻之
剂，不足以抵其巢穴，而当此重任，故立抵当汤。蛭虫之善饮血者，而利于水，□虫
之善吮血者，而猛于陆，并取水陆之善取血者以攻之，同气相求；更佐以桃核之苦温
，推陈致新，大黄之苦寒，荡涤邪热，故名抵当也。若热虽盛而未狂，少腹满而未□
，则宜小其制为丸，以缓治之。若外证已解，少腹急结，其人如狂者，是又为转属阳
明之证，用调胃承气加桃核、桂枝之行血者于其中，以微利之，使胃和则愈矣。此桃
核承气所以为治之缓也。
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伤寒大下后，复发汗，心下痞，恶寒者，表未解也，不可攻痞，当先解表，表解乃可
攻痞。解表宜桂枝汤，攻痞宜大黄黄连泻心汤。
【注】
伤寒大下后，复发汗，先下后汗，治失其序矣。邪热陷入，心下痞结，法当攻里。若
恶寒者，为表未尽也，表既未尽，则不可攻痞，当先解表，表解乃可攻痞。解表宜桂
枝汤者，以其为已汗已下之表也。攻痞以大黄黄连泻心汤者，以其为表解里热之痞也
。
【集注】
『活人书』云：大抵结胸、痞皆应下，然表未解者，不可攻也。
方有执曰：表非初病之表，乃下后复汗，疏缓其表之表也。解犹救也，如解渴、解急
之类是也。解表与发表不同，伤初病之表当发，故用麻黄汤；此以汗后之表当解，故
曰宜桂枝汤。
张璐曰：大下之后复发汗，先里后表，颠倒差误。究竟已陷之邪痞结心下，证兼恶寒
，表邪不为汗衰，即不可更攻其痞，当先行解肌之法以治外，外解已后，乃用大黄黄
连攻其邪热凝聚之痞，方为合法。
【抵当丸方】
水蛭（炒制）二十个，虻虫（炒制，去掉翅膀和足）二十个，桃仁（去掉皮和尖）二十五个，大黄三两。
以上四味药，捣碎过筛，制成四丸。用水一升，煮其中一丸，取汁七合，服用。一昼夜后应当排出瘀血，如果没排出的，再服用。
【集解】
柯琴说：膀胱是腑，血液本来没有地方可以蓄积。少腹部位，是膀胱的居所。热邪结聚导致胀满，应当出现小便不利，反而小便通利的，说明病不在膀胱内部，而在少腹内部。随着经络运行的营血，因为瘀热结聚在少腹里面，而不是膀胱里面。所以虽然小便通利，但少腹胀满急结的症状依旧存在，这是瘀血蓄积在少腹。热邪淫溢于内，神魂不安，所以发狂；血液瘀滞不行，则营血不能运行，所以脉象微而沉；营血不能运行则气机不能宣通，所以脉象沉而结。营气不能周流全身，则身体发黄。消谷善饥，是因为胃火炽盛；大便反而容易排出，是因为血液濡润肠道；大便颜色黑，是瘀血化腐的表现；健忘，是因为血液不能滋养智慧导致神志不明，这些都是瘀血的征象，如果不是极其峻猛的药剂，不足以攻抵其巢穴，承担此重任，所以设立抵当汤。水蛭善于吸血且利于在水中活动，虻虫善于吮血且猛烈于陆地，同时选取水陆两栖中善于取血的生物来攻击瘀血，同气相求；再加上桃仁的苦温之性，推陈致新，大黄的苦寒之性，荡涤邪热，所以名叫抵当。如果热势虽盛但未到发狂的程度，少腹胀满但未到急结的程度，就应当减小剂量改为丸剂，以缓和的方法治疗。如果外证已经解除，少腹急结，病人像发狂一样，这又是转属阳明经的证候，用调胃承气汤加上桃仁、桂枝等行血药物在其中，轻微通下，使胃气和顺就好了。这就是桃核承气汤作为缓和治法的原因。
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伤寒经过剧烈泻下后，又再次发汗，出现心下痞塞感，伴有恶寒症状，说明表证未解，不可攻逐痞结，应当先解表，表证解除后才能攻逐痞结。解表适宜用桂枝汤，攻逐痞结适宜用大黄黄连泻心汤。
【注】
伤寒经过剧烈泻下后，又再次发汗，先泻下后发汗，治疗失去了次序。邪热陷入体内，心下痞结，按照法则应当攻里。如果有恶寒症状，说明表邪未尽。既然表邪未尽，就不可攻逐痞结，应当先解表，表证解除后才能攻逐痞结。解表适宜用桂枝汤，是因为这是已经发汗、已经泻下后的表证。攻逐痞结用大黄黄连泻心汤，是因为这是表解之后里的热邪导致的痞证。
【集注】
《活人书》说：大体上结胸、痞证都应当用下法，但是表证未解的，不可攻逐。
方有执说：这里的表不是初病的表，而是泻下后又发汗，疏缓了体表的表证。解的意思是解救，就像解渴、解急之类。解表与发表不同，伤初病的表应当发散，所以用麻黄汤；这里因为是发汗后的表证应当解救，所以说适宜用桂枝汤。
张璐说：剧烈泻下后又发汗，先治里后治表，顺序颠倒错误。最终已陷入的邪气痞结在心下，证候兼有恶寒，表邪不因发汗而衰减，就不可再攻逐其痞结，应当先行解肌的方法治疗外部，外部解除后，再用大黄黄连攻逐邪热凝聚的痞结，这才是合法的治疗。
[Didang Pill Formula]
Shuizhi (Leech, *Hirudo nipponica*) (stir-fried) 20 pieces, Mengchong (Blue Bottle Fly Larva, *Calliphora vicina* larva) (stir-fried, wings and legs removed) 20 pieces, Tao Ren (Peach Kernel, *Prunus persica* seed) (skin and tip removed) 25 pieces, Dahuang (Rhubarb Root, *Rheum palmatum* root) 3 liang.
The above four ingredients are crushed, sifted, and formed into four pills. Boil one pill in one sheng of water, reduce to seven ge, and administer. Within a day and night, bloody stool should be passed; if not passed, administer again.
[Collected Commentary]
Ke Qin stated: The Bladder is a fu-organ, and blood has no place to accumulate within it. The Shaoyang abdomen (lower abdomen) is the residence of the Bladder. When heat binds causing fullness, urinary difficulty should occur; however, if urination is actually free, it indicates that the disease is not inside the Bladder but within the lower abdomen. The ying-blood traveling along the meridians, due to stasis-heat binding in the interior of the lower abdomen, rather than the interior of the Bladder itself. Therefore, although urination is free, the fullness, urgency, and binding sensation in the lower abdomen remain unchanged, indicating blood stasis accumulating in the lower abdomen. Heat overflowing internally disturbs the shen-spirit, leading to mania; when blood is stagnant and fails to circulate, ying-nutrition cannot transport, resulting in a faint and deep pulse; when ying-nutrition fails to circulate, qi mechanism cannot diffuse, resulting in a deep and knotted pulse. When ying-qi does not circulate throughout the body, jaundice occurs. Excessive digestion with frequent hunger indicates blazing stomach-fire; bowel movements being surprisingly easy to pass indicates lubrication by blood; black stool color indicates transformation of accumulated blood; forgetfulness indicates that blood fails to nourish intelligence, leading to unclear spirit. These are all signs of blood stasis. Only extremely potent medicines are sufficient to attack their nest and shoulder this heavy responsibility; thus, Didang Decoction was established. Leeches are good at drinking blood and thrive in water; fly larvae are good at sucking blood and are fierce on land. By combining these creatures from both water and land that excel at extracting blood, we seek similarity to attract and attack [the stasis], following the principle of "like attracts like." Furthermore, assisted by the bitter-warm nature of Peach Kernels to push out the old and generate the new, and the bitter-cold nature of Rhubarb to sweep away pathogenic heat, it is named Didang. If the heat is severe but has not reached the point of mania, and the lower abdomen is full but not yet urgent and bound, the dosage should be reduced and formulated into pills for slow treatment. If exterior symptoms have resolved, but there is urgency and binding in the lower abdomen, and the patient exhibits manic behavior, this is a syndrome transferring to the Yangming stage. Use Tiao Wei Cheng Qi Decoction added with blood-moving agents such as Peach Kernels and Cinnamon Twig, to induce mild purgation, so that when the Stomach harmonizes, recovery occurs. This explains why Taohao Cheng Qi Decoction serves as a milder treatment method.
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After severe purgation in Cold Damage, followed by repeated sweating, if epigastric stuffiness (pi) occurs accompanied by aversion to cold, the exterior is unresolved. One must not attack the pi directly; instead, resolve the exterior first. Only after the exterior is resolved can the pi be attacked. For resolving the exterior, Guizhi Tang (Cinnamon Twig Decoction) is suitable; for attacking the pi, Dahuang Huanglian Xiexin Tang (Rhubarb and Coptis Heart-Purging Decoction) is suitable.
[Annotation]
In Cold Damage, after severe purgation followed by repeated sweating, the sequence of treatment—purgation first, then sweating—is incorrect. Pathogenic heat sinks inward, causing epigastric pi-binding, which legally requires attacking the interior. However, if aversion to cold is present, it indicates that the exterior pathogen is not fully expelled. Since the exterior is not fully resolved, one must not attack the pi; instead, resolve the exterior first. Only after the exterior is resolved can the pi be attacked. Guizhi Tang (Cinnamon Twig Decoction) is suitable for resolving the exterior because this is an exterior condition existing after prior sweating and purgation. Dahuang Huanglian Xiexin Tang (Rhubarb and Coptis Heart-Purging Decoction) is used to attack the pi because it addresses pi caused by interior heat after the exterior has resolved.
[Collected Notes]
*Huoren Shu* (Book of Vitality) states: Generally, Jie Xiong (Colliding Chest) and Pi (Stuffiness) syndromes should be treated with purgation; however, if the exterior is unresolved, purgation must not be used.
Fang Youzhi stated: The "exterior" here refers not to the initial disease exterior, but to the exterior loosened by subsequent sweating after purgation. "Resolve" means to relieve or save, similar to relieving thirst or emergency. Resolving the exterior differs from releasing the exterior. For the initial exterior of Cold Damage, one should release it using Mahuang Tang (Ephedra Decoction); here, since it is the post-sweating exterior, it should be relieved, hence stating suitability for Guizhi Tang (Cinnamon Twig Decoction).
Zhang Lu stated: Severe purgation followed by sweating represents treating the interior before the exterior, an inverted error. Ultimately, the sunk pathogen binds in the epigastrium, and the syndrome includes aversion to cold. Since the exterior pathogen does not diminish with sweating, one must not further attack the pi. Instead, one should first employ muscle-releasing methods to treat the exterior. Only after the exterior is resolved should Dahuang Huanglian Xiexin Tang (Rhubarb and Coptis Heart-Purging Decoction) be used to attack the pi condensed by pathogenic heat. This constitutes the lawful approach.