时疫下法与伤寒不同∶伤寒下不厌迟，时疫下不厌早；伤寒在下其燥结，时疫在下其郁热；伤寒里证当下，
必待表证全罢；时疫不论表邪罢与不罢，但兼里证即下；伤寒上焦有邪不可下，必待结在中、下二焦，方可下，时
疫上焦有邪亦可下，若必待结至中、下二焦始下，则有下之不通而死者；伤寒一下即已，仲景承气诸方多不过三
剂；时疫用下药至少三剂，多则有一、二十剂者。
时疫下法有六∶结邪在胸上，贝母下之，贝母本非下药，用至两许即解；结邪在胸及心下，小陷胸下之；结邪
在胸胁连心下，大柴胡汤下之；结邪在脐上，小承气汤下之；结邪在当脐及脐下，调胃承气汤下之；痞满燥实，三
焦俱结，大承气汤下之。此外又有本质素虚，或老人，久病，或屡汗、屡下后，下证虽具而不任峻攻者，则麻仁
丸、蜜煎导法、猪胆导法为妙。
下法之轻、重、缓、急，总以见证为主，详列于后。
急下证∶舌干，舌卷，舌短，舌生芒刺，舌黑，齿
燥，鼻如烟煤，胸腹满痛，狂，昏沉，发热汗多，身冷，呃逆。
当下证∶舌黄，谵语，善忘，多言，协热利，头胀痛，烦，躁。
缓下证∶舌淡黄苔，微渴，大便闭，小便黄赤，潮热，齿燥。
以上诸证，缓下者不下，则必渐重而为当下证。当下者缓下，则必加重而为急下证。急下者失下，则虽下之多
不通，而致结热自下逆上，胀满直至心下，又逆上通过膈膜，有至胸满如石，咽喉锯响，目直视反白，或睛盲、瞳
散，耳聋，九窍不通，虽有神丹，莫之能救矣。外更有蓄血、蓄水诸下法，前已散见诸条，兹再详列，以便翻阅。
蓄水证∶小便不利，大便微利。
蓄血证∶小便自利，大便黑。他若蓄水，蓄血在胸胁，不当下者，此不赘。
时疫（流行性温热疫病）使用下法与伤寒不同：伤寒治疗中，使用下法不嫌晚；时疫治疗中，使用下法不嫌早。伤寒的病邪在于体内的燥屎结聚，时疫的病邪在于体内的郁积之热；伤寒必须有里证才可使用下法，且必须等待表证完全解除后才行；时疫不论表邪是否已解，只要兼有里证即可使用下法。伤寒认为上焦有邪气不可使用下法，必须等待病邪结聚在中、下二焦，方可使用下法；时疫即使上焦有邪气也可使用下法，如果一定要等到病邪结聚到中、下二焦才使用下法，就会因为下法不通畅而导致患者死亡。伤寒使用一次下法即可痊愈，张仲景的承气汤类方剂大多不超过三剂；时疫使用下法至少需要三剂，多的有一二十剂的情况。
时疫的下法有六种情况：病邪结聚在胸部上方，用贝母来攻下，贝母本来不是攻下药，但用量达到一两左右即可见效；病邪结聚在胸部及心窝下方，用小陷胸汤来攻下；病邪结聚在胸胁部并连及心窝下方，用大柴胡汤来攻下；病邪结聚在肚脐上方，用小承气汤来攻下；病邪结聚在肚脐处及肚脐下方，用调胃承气汤来攻下；若出现痞塞、胀满、干燥、结实等症状，三焦全部结聚，用大承气汤来攻下。此外，又有体质素来虚弱的人，或老年人、久病患者，或在多次发汗、多次攻下之后，虽然具备使用下法的指征但不能耐受猛烈攻伐的情况，此时使用麻仁丸、蜜煎导法、猪胆导法为妙。
下法的轻、重、缓、急，总以具体的证候表现为依据，详细列举如下。
急下证（需要紧急攻下的证候）：舌面干燥，舌体卷缩，舌体短小，舌面生芒刺，舌色黑，牙齿干燥，鼻孔如烟熏煤黑，胸腹部胀满疼痛，狂躁，昏沉嗜睡，发热且出汗多，身体冰冷，呃逆。
当下证（应当及时攻下的证候）：舌苔黄，说胡话（谵语），健忘，多言，协热利（伴有发热的腹泻），头部胀痛，心烦，躁动不安。
缓下证（可以缓慢攻下的证候）：舌苔淡黄色，轻微口渴，大便闭塞，小便黄赤，潮热，牙齿干燥。
以上各种证候，属于缓下证的如果不进行攻下，病情必然会逐渐加重而转变为当下证。属于当下证的如果采用缓慢攻下，病情必然会加重而转变为急下证。属于急下证的如果错失攻下时机，即使后来使用下法也大多不通畅，导致结聚的热邪从下向上逆行，胀满之气一直延伸到心窝下方，又向上通过膈膜，发展到胸部胀满坚硬如石，咽喉发出像拉锯一样的响声，眼睛直视不能转动或眼白外露，或者眼球失明、瞳孔散大，耳聋，九窍不通，此时即使有神丹妙药，也无法救治了。另外还有蓄血、蓄水等使用下法的情况，前面已在各条文中分散提及，这里再详细列出，以便查阅。
The purgative method for epidemic febrile diseases (Shi Yi, epidemic warm pathogenic diseases) differs from that for cold damage (Shang Han): In the treatment of cold damage, the use of purgatives is not considered too late; in the treatment of epidemic febrile diseases, the use of purgatives is not considered too early. The pathology of cold damage lies in dry fecal impaction within the interior, whereas the pathology of epidemic febrile diseases lies in stagnant heat within the interior; for cold damage, the purgative method is indicated only when there are interior syndromes, and it must be waited until exterior syndromes have completely resolved; for epidemic febrile diseases, regardless of whether exterior pathogens have resolved or not, the purgative method can be used as long as interior syndromes are present. For cold damage, if pathogens are in the Upper Jiao, purgation is contraindicated; one must wait until the pathogens are consolidated in the Middle and Lower Jiao before using purgation; for epidemic febrile diseases, even if pathogens are in the Upper Jiao, purgation can still be used. If one waits until pathogens consolidate in the Middle and Lower Jiao before purging, it may lead to death due to ineffective purgation. A single application of purgation usually suffices for cold damage, and Zhang Zhongjing's Chengqi Decoction formulas are generally prescribed for no more than three doses; for epidemic febrile diseases, the purgative method requires at least three doses, and sometimes up to ten or twenty doses.
There are six types of purgative methods for epidemic febrile diseases: When pathogens are consolidated in the upper chest, Fritillariae Bulbus (Beimu, 贝母) is used for purgation; although Beimu is not typically a purgative herb, a dose of approximately one tael (approx. 37.5g) can achieve the effect. When pathogens are consolidated in the chest and below the heart (epigastrium), Xiaoxianzhong Tang (Small Trap-Resolving Decoction) is used for purgation. When pathogens are consolidated in the chest and hypochondrium extending to below the heart, Dachaihu Tang (Major Bupleurum Decoction) is used for purgation. When pathogens are consolidated above the umbilicus, Xiao Chengqi Tang (Minor Order the Qi Decoction) is used for purgation. When pathogens are consolidated at the umbilicus and below the umbilicus, Tiaowei Chengqi Tang (Regulate the Stomach and Order the Qi Decoction) is used for purgation. When symptoms such as stuffiness, fullness, dryness, and solidity are present, with consolidation throughout the Three Jiaos, Da Chengqi Tang (Major Order the Qi Decoction) is used for purgation. Additionally, for patients with inherent constitutional deficiency, the elderly, those with chronic illnesses, or those who have undergone repeated sweating or purging, where purgative indications are present but they cannot tolerate harsh purgation, Mahuan Wan (Hemp Seed Pill), Mi Jian Dao Method (Honey Suppository Method), and Zhu Dan Dao Method (Pig Gallbladder Suppository Method) are excellent choices.
The lightness, heaviness, slowness, and urgency of the purgative method are always determined by the specific syndrome manifestations, which are detailed below.
Urgent Purgation Syndromes: Dry tongue, curled tongue, short tongue, prickles on the tongue surface, black tongue, dry teeth, nostrils appearing sooty like smoke-coal, abdominal distension and pain, mania, lethargy/coma, fever with profuse sweating, cold body, hiccups.
Indications for Timely Purgation: Yellow tongue coating, delirium (Zhenyu), amnesia, excessive talking, diarrhea accompanied by fever (Xie Re Li), head distension and pain, irritability, restlessness.
Mild Purgation Syndromes: Pale yellow tongue coating, slight thirst, constipation, yellow-red urine, tidal fever, dry teeth.
If the above mild purgation syndromes are not treated with purgation, they will inevitably worsen and transform into timely purgation syndromes. If timely purgation syndromes are treated with mild purgation, they will inevitably worsen and transform into urgent purgation syndromes. If urgent purgation syndromes miss the window for purgation, subsequent purgation will likely fail to clear the bowels. This leads to stagnant heat reversing upward from below, causing distension extending to the epigastrium, then reversing upward through the diaphragm, resulting in chest fullness hard as stone, sawing sounds in the throat, fixed gaze with scleral exposure, blindness, dilated pupils, deafness, and blockage of all nine orifices. At this stage, even divine medicines cannot save the patient. Furthermore, there are other purgative methods for blood accumulation (Xu Xue) and water accumulation (Xu Shui), which have been mentioned scatteredly in previous sections; here they are listed in detail for easy reference.
Water Accumulation Syndrome: Difficult urination, slight loose stools.
Blood Accumulation Syndrome: Normal urination, black stools. Other conditions involving water or blood accumulation in the chest and hypochondrium do not require purgation and are not elaborated upon here.