Jing Da Ji

Euphorbia pekinensis is one of the four herbs (with Gan Sui, Yuan Hua and Hai Zao) that the Eighteen Incompatibilities forbid combining with Gan Cao. Three modern lines of evidence converge. In MDCK renal cells a 1:1 decoction of the two herbs was significantly more cytotoxic than the Euphorbia alone, with 3,3'-di-O-methylellagic acid and its xyloside identified as the responsible compounds acting through reactive oxygen species, loss of mitochondrial membrane potential and apoptosis; raising the licorice proportion above 1:1 reduced the effect, so the interaction is ratio-dependent rather than absolute. In rats using tolbutamide as probe, each herb alone induced CYP2C9 and the combination induced it more strongly, which would lower plasma levels of active constituents of both herbs and of anything else in the prescription. Over 30 days of dosing the pair suppressed butyrate production, blocked the rise in Lactobacillus that licorice alone produced, and further depleted Akkermansia and Butyricimonas that Euphorbia alone already reduced, while raising Streptococcus and Prevotella. Separately, licorice itself causes potassium loss through pseudoaldosteronism, which stacks badly on the fluid and electrolyte loss of a drastic purgative.

Two botanically unrelated drugs are sold under the name Da Ji: Jing Da Ji, the root of Euphorbia pekinensis (Euphorbiaceae), whose activity and toxicity rest on casbane and related diterpenoids, and Hong Da Ji, the root of Knoxia valerianoides (Rubiaceae), whose chemistry is anthraquinone-based. Classical texts frequently use Da Ji for both, and the two were only listed as separate monographs from the 1995 edition of the Chinese Pharmacopoeia onward. Jing Da Ji is the more toxic and the more strongly water-draining; the Pharmacopoeia requires it to be vinegar-processed, whereas Hong Da Ji does not carry the same mandatory processing requirement. Substituting one for the other therefore changes both the dose-toxicity relationship and the preparation the prescription assumed. The batch record for the Knoxia entry in this database carries the Latin name Radix Euphorbiae Pekinensis, which is exactly the conflation described here.

Jing Da Ji is a drastic cathartic that produces watery stools and can drive substantial fluid and electrolyte loss, and the diterpenoids directly injure the intestinal epithelium and disrupt tight junctions. Potassium depletion from any cause increases digoxin binding to Na,K-ATPase and lowers the threshold for glycoside-induced arrhythmia. No study has tested this specific pair, so the mechanism is inferred rather than demonstrated, but it follows from established pharmacology.

The herb is prescribed precisely to drive off accumulated fluid, and it does so by catharsis and diuresis. Layering it on a pharmaceutical diuretic in a patient with ascites or pleural effusion, which is exactly the population it is used in, compounds volume contraction and potassium loss. No controlled study exists for this combination.

Drastic purgatives of this class are contraindicated in pregnancy throughout the classical and modern Chinese literature, on the grounds of violent catharsis and the risk to the pregnancy. The diterpenoid chemistry of the genus Euphorbia includes irritant and tumour-promoting esters, and the herb is directly cytotoxic to intestinal epithelium at low microgram-per-millilitre concentrations.