Alternating chills and fever, hypochondriac fullness and pressure, persistent vomiting, hard distended abdomen, constipation or burning diarrhoea, bitter mouth, restlessness, yellow tongue coating — Western medicine typically classifies this cluster as acute cholecystitis, pancreatitis, or cholelithiasis. In TCM, it represents Shaoyang-Yangming Combined Disease: the Shaoyang pathogen has not resolved, while Yangming Heat-binding has already formed. The liver-gallbladder-Spleen-Stomach Qi dynamic is obstructed; Heat accumulates internally. Two thousand years ago, the Sage of Medicine Zhang Zhongjing wrote the definitive formula for this pattern into the Shang Han Lun and Jin Kui Yao Lüe: Da Chai Hu Tang (Major Bupleurum Decoction). It harmonises the Shaoyang without violating the prohibition against purging a Shaoyang pattern, while simultaneously clearing Yangming Heat-binding — a dual exterior-interior resolution that remains the standard TCM intervention for Liver-Gallbladder-Spleen-Stomach excess-Heat presentations.

I. Classical Origin

Da Chai Hu Tang first appears in the Shang Han Lun: “When a Taiyang disease has passed its course by more than ten days, and repeated purging has been used, and after another four or five days the Chai Hu presentation is still present — first give Xiao Chai Hu Tang. If vomiting does not stop, with epigastric urgency and mild restlessness, this has not resolved; give Da Chai Hu Tang to purge, and it will recover.” The Jin Kui Yao Lüe adds: “When pressure on the epigastrium produces fullness and pain, this is Excess; it should be purged; Da Chai Hu Tang is appropriate.”

The classical mnemonic captures its composition and action: “Da Chai Hu Tang — Qin, Da Huang; Zhi, Shao, Ban Xia, Zao, Sheng Jiang; Shaoyang-Yangming combined disease; harmonising and attacking together, matchless in effect.” The Yi Zong Jin Jian commentary precisely captures its character: “Chai Hu doubled with Sheng Jiang — rapid resolution of the half-exterior; Zhi and Shao with a small dose of Da Huang — gradual clearing of the half-interior. Although it is called purging, it is truly a harmonising formula within the purging category.” Da Chai Hu Tang is structurally Xiao Chai Hu Tang minus Ren Shen and Gan Cao, plus Da Huang, Zhi Shi, and Shao Yao — equivalently viewed as a modified combination of Xiao Chai Hu Tang and Xiao Cheng Qi Tang.

II. Eight-Herb Composition and Formula Analysis

Chief herbs (Jun):

• Chai Hu 15g (original: 8 liang): pungent-bitter, slightly cold; enters Liver, Gallbladder. Harmonises the Shaoyang; resolves the half-exterior. Clears alternating fever-chills, hypochondriac fullness, and bitter mouth. The principal herb for Shaoyang disease; the Ben Cao Gang Mu calls it “the essential herb for soothing the Liver.”
• Da Huang 6g (original: 2 liang): bitter, cold; enters Spleen, Stomach, Large Intestine, Liver. Purges Yangming Heat-binding; clears accumulation and stagnation; relieves abdominal distension and constipation. Used at low dose (6g) for gentle purging of Heat-binding — “attacking without excess aggression.”

Deputy herbs (Chen):

• Huang Qin 9g (original: 3 liang): bitter, cold; enters Lung, Gallbladder, Spleen, Large Intestine. Clears and drains Shaoyang constrained Heat; paired with Chai Hu, amplifies harmonising of Shaoyang; clears bitter mouth and restlessness.
• Zhi Shi 9g (original: 4 pieces, dry-fried): bitter-pungent-sour, slightly cold; enters Spleen, Stomach, Large Intestine. Breaks Qi, disperses accumulation, dissolves Phlegm and stuffiness. Paired with Da Huang, amplifies Heat-purging and Qi-descending; relieves epigastric hardness and abdominal fullness-pain.

Assistant herbs (Zuo):

• Shao Yao 9g (original: 3 liang): bitter-sour, slightly cold; enters Liver, Spleen. Soothes Liver and relieves cramping; paired with Da Huang and Zhi Shi, relieves abdominal pain; paired with Da Zao (sour-sweet generates Yin), protects Yin from Heat damage; prevents excessive purging from depleting righteous Qi.
• Ban Xia 9g (original: half sheng, washed): pungent, warm, toxic; enters Spleen, Stomach, Lung. Harmonises Stomach, descends counterflow, stops vomiting; dissolves Phlegm and dissipates nodules. Used here processed with Sheng Jiang (reducing toxicity while amplifying anti-emetic effect). Targets the persistent vomiting that is a hallmark of this pattern.
• Sheng Jiang 15g (original: 5 liang, sliced): pungent, warm; enters Lung, Spleen, Stomach. Used at a notably higher dose than in Xiao Chai Hu Tang — specifically because vomiting is prominent in this pattern. Powerfully harmonises Stomach, descends counterflow; assists Chai Hu in resolving Shaoyang pathogens; moderates the cold nature of Huang Qin and Da Huang.

Envoy herb (Shi):

• Da Zao 4 pieces (original: 12 pieces, split): sweet, warm; enters Spleen, Stomach, Heart. Supplements Middle Jiao and nourishes Qi-Blood; moderates the bitter-cold of Da Huang and Huang Qin and the Qi-breaking of Zhi Shi; harmonises all herbs toward a more moderate overall action. Notably, this formula uses fewer Da Zao than Xiao Chai Hu Tang — reflecting the shift from tonification-priority to resolution-priority.

Three layers of formula logic:
① Harmonise and purge, resolve both exterior and interior: Chai Hu clears the half-exterior Shaoyang; Da Huang + Zhi Shi purge the half-interior Yangming — one disperses, one descends; simultaneously resolving without violating either principle.
② Move Qi and relieve pain, harmonise Stomach and descend counterflow: Zhi Shi moves Qi and breaks accumulation; Shao Yao soothes Liver and relieves cramping — together addressing hypochondriac pain and abdominal cramping; Ban Xia + Sheng Jiang target vomiting and harmonise Qi flow.
③ Clear Heat and protect Yin, attack without excess aggression: Huang Qin clears Shaoyang constrained Heat; Da Huang lightly purges Yangming Heat-binding — clearing without consuming Yin; Shao Yao + Da Zao (sour-sweet generating Yin) protect body fluids; prevents over-purging from damaging righteous Qi — “attacking without aggression, harmonising without stagnation.”

III. Core Pattern Identification

Shaoyang signs: alternating chills and fever (irregular, not timed); bilateral hypochondriac fullness and pressure (worsened by palpation); bitter mouth, dry throat; dizziness; restlessness; mild depression.

Yangming excess-Heat signs: persistent vomiting (frequent, difficult to relieve); epigastric hardness or fullness-pain (hard on palpation, painful under pressure); constipation (days without defecation) or hot-diarrhoea (sticky stool, burning anus, with fever); yellow greasy or dry-yellow tongue coating; wiry rapid forceful pulse.

The formula is also applicable to Liver-Gallbladder Qi obstruction with excess-Heat accumulation producing hypochondriac pain or jaundice, provided the underlying pattern matches Shaoyang-Yangming combined disease.

IV. Modern Clinical Applications

1. Hepatobiliary disease: acute cholecystitis; chronic cholecystitis acute exacerbation; cholelithiasis; acute cholangitis. Presentation: right upper quadrant pain; bitter mouth; nausea-vomiting; fever; hypochondriac fullness; constipation; yellow tongue coating; wiry rapid forceful pulse. Da Chai Hu Tang relieves pain, clears Heat, and drains Gallbladder. Add: Yin Chen, Zhi Zi (jaundice); Jin Qian Cao (gallstones).

2. Pancreatic disease: acute pancreatitis (Shaoyang-Yangming combined pattern). Upper abdominal severe pain; nausea-vomiting; fever; abdominal distension and constipation. Clinical studies show Da Chai Hu Tang combined with Western medicine for acute pancreatitis significantly reduces symptom duration. Add: Yan Hu Suo, Mu Xiang (severe pain); Mang Xiao (severe constipation).

3. Gastrointestinal disease: acute gastroenteritis; peptic ulcer acute exacerbation; early intestinal obstruction — where upper abdominal pain, nausea-vomiting, abdominal distension, constipation or diarrhoea match the excess-Heat pattern.

4. Other: acute tonsillitis; parotitis (Shaoyang-Yangming combined pattern); Damp-Heat type fatty liver; paediatric high fever with alternating chills, abdominal distension, constipation (paediatric dose: halve Da Huang and Ban Xia).

V. Clinical Modifications

VI. Preparation, Dosage, and Safety

Decoction method: Soak all herbs except Da Huang for 30 min; bring to boil, reduce to simmer 30 min; add Da Huang (last, 5–10 min only — prolonged decoction weakens purgative anthraquinones); strain; re-decoct residue 20 min; combine liquids; take in two warm divided doses, once daily. Da Huang must be added last; Ban Xia should be pre-processed with ginger; Da Zao should be split before decocting.

Course: Acute disease (acute cholecystitis, acute pancreatitis): 3–7 days; stop when symptoms resolve. Chronic disease acute exacerbation: 1–2 courses (7–14 days), then reassess. Do not self-prescribe long-term — sustained cold-natured and Qi-breaking herbs damage Spleen-Stomach over time.

Patent medicine: Da Chai Hu Tang pill is available; typically 9g twice daily with warm water; follow prescriber’s instructions or product insert. Also available as Da Chai Hu Tang granules; search for Da Chai Hu formulations.

Contraindicated populations:

• Pregnant women: Da Huang has Blood-activating and purgative effects; Zhi Shi breaks Qi; Ban Xia is classified as toxic — use only under strict medical supervision
• Constitutionally weak, Blood-Qi deficient patients: use cautiously; reduce doses of Da Huang and Zhi Shi under medical guidance
• Known allergy to any component: contraindicated

Monitoring during treatment: frequent loose stool or intensifying abdominal pain → likely excess Da Huang; stop immediately and reassess. Nausea, dizziness → possible Ban Xia or Zhi Shi sensitivity; stop and consult. Never self-prescribe Da Chai Hu Tang for acute abdominal presentations without confirmed TCM pattern diagnosis; if severe abdominal pain, persistent high fever, vomiting with inability to keep fluids down, or respiratory distress occurs — seek emergency medical care. TCM formulas are adjuncts, not replacements, for acute surgical emergencies.

Conclusion

Da Chai Hu Tang’s 2,000-year clinical persistence reflects a genuine pharmacological insight: Shaoyang-Yangming combined disease requires simultaneous harmonising and purging; neither approach alone is sufficient. The formula’s design — Chai Hu and Huang Qin for the Shaoyang half, Da Huang and Zhi Shi for the Yangming half, Shao Yao and Da Zao protecting Yin and moderating the attack, Ban Xia and Sheng Jiang targeting vomiting — produces a balanced resolution that attacks without over-attacking and harmonises without leaving stagnation. He Lianchen’s summary in Chong Ding Tong Su Shang Han Lun remains accurate: “A good harmonising formula for Shaoyang-Yangming — its strength lies above Xiao Chai Hu Tang’s, which is why it is called Da (Major).” The formula’s modern wellness relevance: the pattern it addresses — Liver-Gallbladder Qi stagnation with Stomach-Intestinal excess-Heat — arises from exactly the lifestyle factors most prevalent today: late nights, oily-spicy diet, chronic stress, and physical inactivity. Use this formula correctly within its pattern; do not use it as a general Heat-clearing or purgative. Always under qualified TCM practitioner supervision.