Source 出处 · Shanghan Lun · Doses are not given here: they are set by a licensed practitioner for the individual.
Safety. Fu Zi Tang is recorded in the Shao Yin section of the Shanghan Lun in two short lines. The first: 少阴病，得之一二日，口中和，其背恶寒者，当灸之，附子汤主之 — in the first day or two of a Shao Yin disorder, when the mouth is neutral and the back is cold, apply moxa; Fu Zi Tang governs it. The second: 少阴病，身体痛，手足寒，骨节痛，脉沉者 — body pain, cold hands and feet, joint pain, a deep pulse.
The name is both the whole problem and the whole interest. 附子 is processed aconite daughter root, and aconitine and the related alkaloids are among the most acutely toxic substances in the materia medica. The reported picture is paraesthesiae of the mouth and limbs progressing to ventricular arrhythmia and asystole, and poisoning from improperly processed root and from home-prepared preparations is reported regularly. This entry records the hazard and deliberately does not record any method for reducing it, because a reader who intends to handle this root needs a pharmacopoeia and a licensed supplier, not a knowledge base. It is also worth saying that 附子 is not 白附子, which is a Typhonium rhizome: different plant, different traditional use, and the names are close enough to be dangerous. Several Aconitum species are used regionally, and their alkaloid content is not comparable.
The second thing worth saying is that the person the text describes — cold back, cold hands and feet, aching body and joints, no fever mentioned, a deep pulse — is a person a modern clinician would also stop and look at closely, though not for the reason the text does. Coldness, body aches and profound fatigue without fever is how sepsis presents in older adults and in people who are immunocompromised; hypothermia rather than fever is a recognised marker of worse outcome, and its absence is not reassurance. The same cluster covers hypothyroidism, anaemia, adrenal insufficiency, hypoperfusion from any cause, and the first two days of influenza and other viral illness in an adult, in which myalgia and chills dominate and fever may never appear or may already have passed. Aching limbs and shoulders with stiffness in a person over fifty also raises polymyalgia rheumatica, which is a working diagnosis made on blood tests and response, and which carries a specific association with giant cell arteritis and risk of sight loss. None of these is excluded by a deep pulse.
Two further things belong on the page. First, 附子汤 is not the only formula carrying this name: the Jingui Yaolüe also mentions a 附子汤 in the pregnancy chapter, and its original composition is not transmitted. This entry takes the five-ingredient Shanghan Lun version and does not adjudicate between them. Second, 人参 is named in the classical 十八反 against 藜芦 (Veratrum) and in the 十九畏 against 五灵脂; it is not 党参, not 西洋参 and not 红参, and its interaction literature — with warfarin in particular — is substantial enough that a person on anticoagulants should not add it without telling whoever manages that medicine.
Fu Zi Tang is recorded here because it is the clearest statement in the classical corpus of what "cold" meant as a clinical picture. It is also the clearest case of a picture that today means: take a temperature, take a set of observations, and keep watching — rather than warm the person up.
附子汤在《伤寒论》少阴病篇，只有短短两条。其一：少阴病，得之一二日，**口中和，其背恶寒**者，当灸之，附子汤主之。其二：少阴病，**身体痛，手足寒，骨节痛，脉沉**者，附子汤主之。
方名就是全部的问题，也是全部的看点。**附子是炮制后的乌头子根**，乌头碱及其同类生物碱是本草中急性毒性最强的一类物质：报道的表现是口唇与四肢麻木起病，进而室性心律失常、心搏停止；因炮制不当或自行制备而中毒的病例在持续被报道。本条记录这个危害，并**刻意不记录任何降低危害的方法** —— 想要处理这味药的人需要的是药典和有资质的供应渠道，而不是一个知识库。还要说清：**附子不是白附子**（独角莲的块茎），两者植物来源不同、传统用途不同，而名字近到足以出事；不同地区使用多种乌头属植物，其生物碱含量并不可比。
第二件值得说的是：条文描述的这个人 —— 背恶寒、手足寒、身体骨节痛、未提发热、脉沉 —— 今天的临床医生同样会停下来仔细看，只是理由不同。**畏寒、身痛、极度乏力而不发热，正是脓毒症在老年人与免疫受损者身上的起病方式**；低体温而不是发热是公认的预后不良标志，「没有发烧」不是让人安心的证据。同一组表现还覆盖甲状腺功能减退、贫血、肾上腺皮质功能不全、任何原因的低灌注，以及成人流感等病毒感染的头两天 —— 那时肌痛与寒战占主导，发热可能始终不出现，或已经退了。五十岁以上的人出现肩背四肢酸痛伴僵硬，还要考虑风湿性多肌痛，那是靠血沉/CRP 与治疗反应作出的临床诊断，并且与巨细胞动脉炎及失明风险有明确关联。这些，脉沉一条都排除不了。
还有两点要写：**附子汤一名对应不止一首方** —— 《金匮要略》妇人妊娠篇亦记有附子汤，而其原方组成未传。本条取《伤寒论》五味版，不裁决二者。其次，**人参**在十八反中与藜芦相对、在十九畏中与五灵脂相对；它**不是党参、不是西洋参、不是红参**；它与华法林等的相互作用文献是实在的 —— 正在服用抗凝药的人若要加用，必须让管理那张处方的人知道。
收录附子汤，是因为它是古典文献里对「寒」作为一组临床见症最清晰的陈述；也因为它同时是最清晰的一个例子：这组见症在今天意味着量体温、做观察、持续监护，而不是把人捂热。