Semen Euphorbiae Lathyridis — the ripe seed of Euphorbia lathyris L. (caper spurge, mole plant, 续随子; family Euphorbiaceae). Its de-fatted seed cake is the related material 千金子霜.
Nature and flavour. Acrid, warm, toxic. Liver, Kidney and Large Intestine systems.
This belongs on the drastic shelf of the purge category, alongside 甘遂, 大戟 and 芫花 — the drugs the classical literature treats as weapons rather than as remedies. The sources record it for severe oedema and ascites and for abdominal fluid accumulation, and externally for warts and stubborn sores. Two things should be said plainly. First, the traditional handling already treats it as a poison with a narrow window: the standard material is the de-fatted cake, because the seed oil carries both the purgative and the irritant fraction, and the classical texts are explicit that this is a drug used once and then stopped. Second, and more important for a modern reader: expelling water by purging is a pre-modern description of what is physiologically a violent loss of fluid. It does not address heart failure, kidney failure, cirrhosis or nephrotic syndrome, which are the things that actually cause oedema, and treating them by purgation delays the care that works. This page exists because the drug is in the classical record, not because anyone should reach for it.
性味归经。辛，温，有毒。归肝、肾、大肠经。
它属于泻下药里峻烈的一格，与甘遂、大戟、芫花同列——古典文献把这些药当兵器而不是当补药。文献记载其用于重症水肿、腹水与腹中水饮停聚，外用治疣赘与顽癣恶疮。有两件事应当说清楚。其一，传统处理本就把它当作窗口极窄的毒药：标准用药是去油的霜，因为种子油同时带着泻下与刺激两部分，而古籍明确说这是一用即止的药。其二，对现代读者更要紧：以泻下「逐水」是对剧烈失水的前现代描述。它不处理心衰、肾衰、肝硬化或肾病综合征——那才是水肿的真正成因；用泻法去治，只会耽误真正有效的治疗。这一页之所以存在，是因为这味药在古典记录里，而不是因为谁该去用它。
有毒，机制并不玄：种子尤其是种子油含巨大戟二萜醇与千金二萜醇一类的刺激性二萜酯，正是这类成分使大戟属乳汁成为众所周知的可致皮炎与眼部化学性损伤的物质。吞服后表现为口腔灼痛、剧烈呕吐、绞痛与大量水泻，随之而来的是脱水与电解质丢失；已有严重乃至致死性中毒的报告。此类二萜酯在实验体系中显示促肿瘤活性，这也是把该植物民间用于疣与皮肤病灶只算民间做法、不算家庭疗法的原因之一。孕期一律禁用——它是传统的堕胎药，而孕期正是风险最不可接受的场景；哺乳期、儿童、体弱者，以及心、肾、肝病或已脱水者同样禁用。不要碾碎种子，也不要徒手处置新鲜植株，并远离眼睛；该植物在一些国家被当作驱鼹植物出售，在另一些国家属入侵种，多数人就是这样遇到它的。任何疑似摄入都属中毒急救或急诊范畴，就医时应把原包装一并带上。这类药在现代实践中只属于受过训练的专业者与药典——如果还用的话。