Gancao Mahuang Tang (Licorice and Ephedra Decoction) gān cǎo má huáng tāng · 甘草麻黄汤

Safety. Two ingredients, and the line that records it is shorter than this sentence: 里水，甘草麻黄汤亦主之. Interior water; licorice and ephedra also govern it. The 里水 this line refers to is described earlier in the same chapter: the whole body, the face and the eyes swollen and yellow, the pulse deep, the urine scanty. That is worth reading slowly, because each of the three clauses has a counterpart today that is measured rather than interpreted. Swelling of the whole body including the face is generalised oedema, and the mechanism list is short — heart, kidney, liver, albumin, medicine. A deep pulse has no counterpart, and this library does not pretend that it does. Scanty urine, however, is the clause with a clock in it: reduced urine output in someone who is oedematous is oliguria, and oliguria is how acute kidney injury first presents. Serum creatinine, urine output and obstruction of the urinary tract are checked within hours rather than weeks, and the obstruction part is not exotic — an enlarged prostate, a stone, a pelvic mass — and it is reversible when it is found. The second thing that deserves to be said plainly concerns the two ingredients themselves, because this is one of the very few formulas in this library in which every ingredient pushes in the same direction on the same measurement. Ephedra contains ephedrine-type alkaloids, which are sympathomimetic amines: they raise blood pressure and heart rate, they cause insomnia and tremor, and they can cause urinary retention. They interact with monoamine oxidase inhibitors and with medicines for blood pressure. Ephedra appears on prohibited lists in sport. In 2004 the United States food and drug regulator banned ephedra-containing dietary supplements after a review of cardiovascular and nervous system events, and that ban is the reason this paragraph exists. Licorice raises blood pressure by a different route entirely: glycyrrhizin produces a state resembling excess mineralocorticoid, with salt and water retention, potassium loss and raised blood pressure, reported at ordinary amounts over weeks. A formula of two ingredients can therefore raise blood pressure by two independent mechanisms, and in a person who is oedematous, likely to be given a diuretic, and possibly already taking an antihypertensive, that is not a detail. Neither ingredient here is a neutral filler, and neither is a small one by effect. Pregnancy is an absolute exclusion. Chinese-language literature reports observations of this pair in oedema; the studies are small in scale, and this library does not convert them into a claim of established benefit.