Shi Pi San (Spleen-Fortifying Powder) shí pí sǎn · 实脾散

Safety. Shi Pi San is recorded in Jisheng Fang, Yan Yonghe's thirteenth-century formulary. The name is unusually direct: firming the spleen. It belongs to the tradition's category of yin oedema — swelling that is chronic, pitting, worse below the waist, and accompanied by fullness rather than heat. The reasoning built into it is that water collects because the fire that should move it has gone low, and so it pairs warming with draining rather than draining alone. Three things in the composition deserve comment. Fu zi and gan jiang stand at the front: this is a formula that opens by restoring warmth. Around them sit hou po, mu xiang, cao guo ren and da fu pi, all of which move qi — the tradition's insistence that water will not move unless qi moves first is written into the composition itself. And the formula is named for fortifying while being built largely out of herbs that drain. Oedema is, however, the symptom with the longest modern differential and the highest cost of getting it wrong. Bilateral leg oedema has cardiac, renal, hepatic, nutritional and drug causes — calcium channel blockers, NSAIDs, corticosteroids and some glucose-lowering medicines are common culprits — while unilateral swelling with pain is a deep vein thrombosis until excluded. New or worsening breathlessness alongside oedema is a heart-failure pathway, not a constitutional one. Nephrotic syndrome, cirrhosis and hypoalbuminaemia all present as swelling, and none of them is recognised by pulse or tongue. This is a draining formula: someone already taking a diuretic medicine has a fluid balance that a second draining agent disturbs. Safety is the reason to read this entry twice. Fu zi is the most consequential herb in the Chinese materia medica: its aconitine alkaloids hold sodium channels open, and poisoning runs from numbness through ventricular arrhythmia to asystole. It is used only prepared and only after prolonged decoction, which hydrolyses the diester alkaloids; neither step is negotiable, and the margin is not wide. Shi pi san is a powder, and a powder is decocted for a shorter time than a full decoction, so the hydrolysis step deserves particular attention here. Mu xiang must not be confused with qing mu xiang, the Aristolochia root withdrawn because of aristolochic acid nephropathy; true mu xiang is Saussurea costus, listed in CITES Appendix I. Da fu pi is areca peel from the betel palm, and areca nut itself is classified by IARC as carcinogenic to humans. Mu gua is Chaenomeles, the Chinese quince, not the tropical papaya sold under the same English word. Zhi gan cao — honey-fried licorice — carries the pseudoaldosteronism syndrome of sodium and water retention with potassium loss, which is a real tension inside a formula for fluid retention, and is better named than smoothed over. This entry makes no claim that the formula treats heart failure, nephrotic syndrome or any named disease.