Ma Huang Fu Zi Xi Xin Tang (Ephedra, Aconite and Asarum Decoction) má huáng fù zǐ xì xīn tāng · 麻黄附子细辛汤

Safety. Ma Huang Fu Zi Xi Xin Tang is recorded in Shanghan Lun, in the chapter on the lesser yin. The line is unusually short and unusually precise: in lesser yin disease, at its onset, there is fever instead of the expected absence of it, and the pulse is deep; this formula governs it. Three herbs, and the whole interest lies in the two words that make the sentence difficult. Fever normally belongs to an exterior pattern, and an exterior pulse is floating. A deep pulse says the interior is not holding. The text is therefore describing a person who is showing a surface sign while the inside is failing, and it refuses to treat the surface alone. What makes this entry uncomfortable to write is that all three herbs are among the most heavily regulated herbs in the English-speaking world, and they are regulated for three entirely different reasons. Ma huang contains ephedrine alkaloids. In 2004 the United States Food and Drug Administration concluded that dietary supplements containing ephedrine alkaloids were adulterated, and they have not been lawfully sold there since; the World Anti-Doping Agency prohibits them. As a sympathomimetic, ephedra raises blood pressure and heart rate, and it is the wrong class of substance in heart failure, uncontrolled hypertension, arrhythmia, phaeochromocytoma, narrow-angle glaucoma, prostatic obstruction and thyrotoxicosis, and dangerous together with monoamine oxidase inhibitors or other stimulants. Fu zi is aconite: its aconitine alkaloids hold sodium channels open, and poisoning runs through paraesthesia and vomiting to cardiac arrest. Decoction is not decorative here — prolonged boiling hydrolyses the diester alkaloids, and both proper processing and adequate boiling time are non-negotiable. Xi xin belongs to Aristolochiaceae and contains aristolochic acid, which is nephrotoxic and carcinogenic, with cumulative exposure and no established safe threshold; that is why the pharmacopoeia restricts it to root and rhizome, and never to the aerial parts. A modern reader needs the differential stated plainly. Fever in an old, frail or immunosuppressed person is not a mild event: sepsis, pneumonia, urinary infection and meningitis all begin this way. Fever with headache, neck stiffness, altered consciousness or a non-blanching rash belongs on an emergency pathway, and the old may show hypothermia or confusion instead of fever. This library does not claim the formula reduces fever, treats infection, or treats any specific disease.