Source 出处 · Wenbing Tiaobian · Doses are not given here: they are set by a licensed practitioner for the individual.
Safety. Sha Shen Mai Dong Tang is recorded in the Wenbing Tiaobian for the situation its title names: 燥伤肺胃阴分, injury by dryness to the yin of the lung and stomach. The picture is a dry throat, thirst, heat that will not fully settle, and — the symptom that carries the formula — 干咳少痰, a dry cough with scant sputum. It is one of the most frequently quoted formulas in the Chinese tradition for cough after a febrile illness, and it is worth being precise about what a dry cough is today.
Cough lasting more than eight weeks is called chronic, and its common causes are not dryness: upper airway cough syndrome from the nose and sinuses, asthma and non-asthmatic eosinophilic bronchitis, reflux, ACE inhibitor medicine, chronic obstructive pulmonary disease, bronchiectasis, interstitial lung disease, and post-infectious cough that simply outlasts the infection. Lung cancer sits on that list, and the features that move a dry cough from reassurance to imaging are the ones worth knowing: new onset in a person over about forty, a smoker or former smoker, blood in the sputum, hoarseness, unexplained weight loss, or a cough that changes character rather than settles. A dry cough is also a well-recognised adverse effect of a class of blood pressure medicine, which is worth checking before attributing it to a climate or a season.
One ingredient requires a longer note than the others. 天花粉 is the root of Trichosanthes kirilowii — the same plant that gives 瓜蒌, 瓜蒌皮 and 瓜蒌仁, but a different part and a different substance, and despite the name it is not pollen. Two facts about it are documented and neither is minor. First, trichosanthin, the ribosome-inactivating protein isolated from this root, was developed and used in China as an abortifacient, including for termination of pregnancy and for ectopic pregnancy; pregnancy is therefore an absolute exclusion, not a caution. Second, injectable trichosanthin preparations have produced anaphylactic shock, and hypersensitivity to Trichosanthes is reported. Readers who know this root only as a moistening herb tend to be surprised by both.
Three smaller identity points. 生扁豆 is hyacinth bean (Lablab purpureus); like other pulses it contains saponins and a phytohaemagglutinin, and raw or undercooked bean of this kind causes nausea, vomiting and diarrhoea, so it is thoroughly cooked for use. 桑叶 is the leaf of white mulberry, Morus alba — distinct from 桑白皮 (root bark), 桑枝 (twig) and 桑葚 (fruit), which are different parts with different uses. 甘草 here is the unprepared root, and liquorice contains glycyrrhizin: sustained intake produces a mineralocorticoid-like picture of sodium and water retention, potassium loss and raised blood pressure, and potassium loss is the mechanism by which it becomes dangerous alongside digoxin or a thiazide or loop diuretic. The two moistening roots carry the same caveat as elsewhere in this library: 沙参 covers two unrelated plants, and 麦冬 has two official species.
This formula is recorded here as a document of the 燥 concept and how a classical text reasoned from it. It is not a way of deciding what a persistent cough is.
沙参麦冬汤著录于《温病条辨》，方名即已点出场合：**燥伤肺胃阴分**。表现是咽干、口渴、身热缠绵不退，以及承载着这首方的那个症状 —— **干咳少痰**。它是传统里治热病后咳嗽被引用得最多的方之一，而「干咳」在今天是什么意思，值得说准。
**咳嗽超过八周称为慢性咳嗽**，常见原因并不是「燥」：鼻与鼻窦来源的上气道咳嗽综合征、哮喘与非哮喘性嗜酸粒细胞性支气管炎、胃食管反流、ACE 抑制剂这类药、慢性阻塞性肺疾病、支气管扩张、间质性肺病，以及单纯拖过了感染期的感染后咳嗽。**肺癌也在这一串里**；而把干咳从「宽慰」推向「影像」的那些特征值得记住：四十岁以后新发、吸烟或曾吸烟、**痰中带血**、声音嘶哑、不明原因体重下降，或咳嗽性质变了而不是在好转。另外，干咳本身是一类降压药公认的不良反应 —— 在把它归给气候或季节之前，先核对一下用药。
有一味药需要比其它几味多写几句。**天花粉**是栝楼的根 —— 与**瓜蒌、瓜蒌皮、瓜蒌仁**同一株植物，但部位不同、物质不同，而且**它不叫花粉就不是花粉**。关于它有两件事是有记载的，都不是小事：其一，从这味根里分离出的**天花粉蛋白**是一种核糖体失活蛋白，在中国曾被开发并用于**终止妊娠**，包括引产与异位妊娠，所以**孕期是绝对排除项**，而不是「谨慎」；其二，天花粉注射制剂曾引起**过敏性休克**，对栝楼属的过敏反应亦有报道。只知道它是「润燥药」的读者，往往对这两点都感到意外。
另外三个辨物点：**生扁豆**是扁豆（Lablab purpureus），与别的豆类一样含**皂苷与植物凝集素**，生品或夹生会引起恶心、呕吐与腹泻，所以须熟透入药；**桑叶**是桑（Morus alba）的叶，与**桑白皮**（根皮）、**桑枝**（嫩枝）、**桑葚**（果穗）是同一株的不同部位、用途各异；方中**甘草**是生品，而甘草含**甘草酸**：持续摄入可产生盐皮质激素样表现（钠水潴留、失钾、血压升高），失钾正是它与地高辛或噻嗪类/袢利尿剂同用时变危险的机制。两味润药沿用本库它处的提示：**沙参**对应两种毫不相干的植物，**麦冬**有两个法定来源。
本方在这里是作为「燥」这一概念与古典思路的一份记录被收录。它不是判断一个持续咳嗽是什么的办法。