Constipation resists simple solutions. A laxative that works by irritant-purging produces short-term results but damages the intestinal mucosa with sustained use, creating Qi-depletion that worsens the underlying constipation. Li Dongyuan’s Run Chang Wan (Moisten the Intestines Pill), first recorded in Pi Wei Lun (Treatise on the Spleen and Stomach), was created precisely to avoid this failure mode. As the founder of the “Spleen-Stomach school,” Li Dongyuan understood that most chronic constipation in his clinical population arose from the combination of intestinal fluid depletion (Blood deficiency, Yin insufficiency), Blood Stasis obstructing intestinal circulation, and some degree of Heat-accumulation in the bowel — not from a simple excess needing to be purged. His formula’s response: moisten with oil-rich seeds (Huo Ma Ren, Tao Ren), nourish and activate Blood (Dang Gui, Tao Ren), dispel intestinal Wind-Heat and raise Spleen-Yang Qi (Qiang Huo), and drain accumulated Heat gently (Da Huang in small processed dose). The result is constipation relief without depletion of righteous Qi.

I. Historical Source and Multiple Formula Versions

Run Chang Wan is first recorded in Pi Wei Lun attributed to Li Dongyuan (Jin Dynasty). Subsequent generations produced important variations recorded in Shen Shi Zun Sheng Shu, Qi Xiao Liang Fang, and Ren Zhai Zhi Zhi, each adapting the formula for different constipation sub-types. The three most clinically significant versions:

• Pi Wei Lun original version: Huo Ma Ren, Tao Ren, Dang Gui Shao (tail of Dang Gui), Qiang Huo, Da Huang. Attack-and-supplement combined; suited for constipation with Wind-Heat intestinal pattern and Blood-deficiency-Stasis combined. Classic presentation: dry hard pellet-like stool, abdominal distension and pain, oral dryness and bitterness, red tongue with yellow coating.
• Shen Shi Zun Sheng Shu version: Dang Gui, Sheng Di, Zhi Ke, Tao Ren, Huo Ma Ren. Emphasises Yin-nourishing and Blood-supplementing; removes Qiang Huo and Da Huang, adds Sheng Di (Yin-cooling) and Zhi Ke (Qi-moving). Suited for post-partum, post-surgical, or constitutional Blood-deficiency intestinal dryness without significant Heat. Classic presentation: dry stool, pallor, dizziness, palpitations, fatigue.
• Modern clinical version: adds Bai Shao and Yu Li Ren to the original base; Bai Shao nourishes Blood, relieves abdominal cramping, and moderates Da Huang’s purgation; Yu Li Ren enhances oil-润-moistening action. Broader applicability across constitutional types.

The formula’s name — Run Chang (Moisten the Intestines) — directly states its therapeutic character:润 (run, to moisten/lubricate) is the operative mechanism, not 下 (xia, to purge downward).

II. Five-Herb Composition and Formula Analysis (Pi Wei Lun Version)

Modern clinical reference doses: Huo Ma Ren 12–15g · Tao Ren 9–12g · Dang Gui 9–12g · Qiang Huo 6–9g · Da Huang 3–6g (processed; add last 5–10 min). Original pill preparation: grind to fine powder, mix with honey, form into pills. Modern: water decoction, 2 daily doses, or patent pill form.

Chief herb — Huo Ma Ren (Hemp seed) 12–15g: sweet, neutral; enters Spleen, Stomach, Large Intestine. Moistens the Intestines and promotes defaecation, nourishes Yin and supplements fluids. Huo Ma Ren is rich in plant oils (approximately 30–35%) that lubricate the intestinal mucosa and soften dry stool directly. Its sweet-neutral quality neither depletes Qi nor heats the body — it purely moistens. Unlike irritant laxatives, Huo Ma Ren does not stimulate peristalsis through mucosal irritation; instead it reduces the friction coefficient of hardened stool, making voluntary defaecation possible with normal muscular effort. Appropriate for long-term use without creating dependency.

Deputy herbs — Tao Ren and Dang Gui:

• Tao Ren (Peach kernel) 9–12g: bitter-sweet, neutral; enters Heart, Liver, Large Intestine. Activates Blood and disperses Stasis, moistens Intestines and promotes defaecation. Like Huo Ma Ren, Tao Ren is oil-rich and provides mechanical lubrication. But its primary additional role is Blood-Stasis resolution: intestinal obstruction from chronic constipation often involves impaired Blood circulation in the intestinal wall, producing fixed pain, dark tongue, and a feeling of incomplete evacuation even after defaecation. Tao Ren resolves this Stasis while simultaneously moistening. Its mild bitter-descending quality also assists peristalsis.
• Dang Gui 9–12g (traditionally Dang Gui “tail” — the most Blood-activating portion): sweet-pungent, warm; enters Liver, Heart, Spleen. Supplements Blood and activates Blood, moistens Intestines and relieves pain. Dang Gui’s dual function is essential to the formula’s root-treatment action: “Blood deficiency leads to fluid insufficiency; fluid insufficiency leads to intestinal dryness; intestinal dryness leads to constipation.” By supplementing Blood, Dang Gui restores the fluid substrate that keeps intestinal mucosa moist, addressing the constitutional root. Its Blood-activating quality also unblocks intestinal circulation. The classical principle: blood-supplement to restore intestinal moisture (补血润肠).

Assistant herb — Qiang Huo 6–9g: pungent-bitter, warm; enters Bladder, Kidney. Dispels Wind-Damp, scatters Cold and relieves pain. Qiang Huo’s role is the formula’s most frequently questioned element. Li Dongyuan’s theoretical justification: “Wind pathogen easily injures fluids” (风伤津) — when Wind-Heat invades the Large Intestine, it desiccates intestinal fluids, producing dry stool. Qiang Huo expels this Wind-Heat pathogen, removing the cause of fluid depletion. Additionally, Wind naturally promotes movement (风能动气), and Qiang Huo’s Wind-dispelling action assists intestinal Qi movement and peristalsis, restoring the Large Intestine’s transmission function. It also raises Spleen-Yang Qi — supporting the Spleen’s role in fluid generation and distribution.

Envoy herb — Da Huang 3–6g (processed; add last 5–10 min): bitter, cold; enters Stomach, Large Intestine, Liver. Purges Heat and promotes defaecation, cools Blood and detoxifies, disperses Stasis. Da Huang in Run Chang Wan differs critically from Da Huang in Da Cheng Qi Tang: (1) dose is very small (3–6g vs 12g); (2) it is processed (wine-processed or honey-processed Da Huang, which moderates purgative potency); (3) it is added late in decoction (last 5–10 min), reducing bitter glycoside concentration. Its role here is not peak purgation but gentle Heat-draining and Stasis-moving, providing a mild laxative boost alongside the formula’s primary oil-润-moistening mechanism. Dang Gui’s warm nature and Qiang Huo’s pungent-warm nature buffer Da Huang’s cold, maintaining the formula’s overall thermal neutrality.

Four-layer formula logic:
① Moisten (Huo Ma Ren + Tao Ren): oil-based lubrication of dry intestinal mucosa and hard stool — the primary symptom-relief mechanism
② Nourish Blood (Dang Gui + Tao Ren): restore the Blood-fluid substrate that maintains mucosal moisture — the root treatment
③ Dispel Wind-Heat and assist movement (Qiang Huo): remove the intestinal Wind-Heat pathogen depleting fluids; assist peristalsis through Wind-promoting action
④ Drain Heat gently (small-dose processed Da Huang): mildly clear accumulated intestinal Heat and assist Stasis resolution without depleting righteous Qi

III. Clinical Applications and Modifications

Core pattern: Blood-deficient intestinal dryness constipation
Dry, hard, pellet-like stool; difficult or painful defaecation; extended interval between bowel movements; sensation of incomplete evacuation; pale or sallow complexion; dizziness; fatigue; pale or slightly red tongue with thin coating; thin or thin-wiry pulse. Some patients also have oral dryness, lower abdominal distension, or mild pain.

1. Chronic constipation in the elderly: the formula’s optimal population — Qi-Blood progressive depletion with ageing depletes intestinal fluid reserves and weakens peristaltic force. Run Chang Wan addresses both without the risks of irritant laxatives. Modifications: Qi deficiency prominent (breathlessness, prolapse tendency) → add Huang Qi 15–20g, Dang Shen 15g; dry mouth → add Mai Dong 12g, Sheng Di 12g.

2. Post-partum constipation: Blood loss in delivery depletes intestinal fluid. Shen Shi Zun Sheng Shu version (without Qiang Huo and Da Huang; adding Sheng Di and Zhi Ke) is preferred for post-partum use. Modifications: add Bai Shao 15g, Yu Li Ren 12g; Blood Stasis component (lochia retention) → maintain Tao Ren and consider adding Yi Mu Cao 15g.

3. Post-surgical constipation: anaesthesia and surgery deplete Qi-Blood and impair intestinal Qi-movement. Gentle moistening approach preferable to stimulant laxatives. Modifications: add Zhi Ke 9g, Hou Po 9g to assist Qi-movement recovery.

4. Haemorrhoid-associated constipation: dry hard stool worsens haemorrhoid inflammation and bleeding; Run Chang Wan softens stool, reduces straining, and Tao Ren + Dang Gui’s Blood-activating action may reduce haemorrhoid congestion. Modifications: add Di Yu 10g, Huai Hua 12g (haemorrhoid bleeding).

5. Functional constipation in Yin-deficiency constitution: chronic late nights, fever illness, or prolonged dryness depleting body fluids. Modifications: add Xuan Shen 10g, Sheng Di 12g, Huo Ma Ren increase.

Common modifications:

• Qi deficiency (fatigue, breathlessness, organ prolapse tendency): add Huang Qi 15–30g, Dang Shen 15g; remove Da Huang to avoid further Qi depletion
• Intestinal dryness severe (Yin deficiency): add Sheng Di 12g, Mai Dong 12g, Xuan Shen 10g
• Heat prominent (oral bitterness, abdominal pain, red tongue, yellow coating): increase Da Huang to 6–9g; add Zhi Zi 9g
• Qi stagnation prominent (abdominal bloating, belching): add Zhi Ke 9g, Mu Xiang 9g
• Post-partum or post-surgical (Blood deficiency, no Heat): use Shen Shi version (remove Qiang Huo and Da Huang; add Sheng Di, Zhi Ke)

IV. Usage, Dosage, and Safety

Preparation: pill form (original): take before meals with warm water. Decoction: add Da Huang last (5–10 min before removing from heat). Patent forms: Hai Tian Run Chang Wan and Nong Ben Fang Run Chang Wan.

Contraindications: pregnant women (Tao Ren and Da Huang have uterine-stimulating effects; contraindicated in pregnancy); severe diarrhoea or loose stool — formula is for constipation only; Spleen-Stomach Cold deficiency with cold abdomen and loose stool — reduce or eliminate Da Huang; Yang deficiency constipation (cold hands and feet, cold lower abdomen, pale tongue — requires warming laxatives, not moistening); allergy to any component.

Pattern specificity: Run Chang Wan is for intestinal-dryness, Blood-deficiency constipation. It will not help: (1) excess-Heat constipation requiring Da Cheng Qi Tang-level purgation; (2) Qi-deficiency constipation where the bowel lacks the muscular force to expel (needs Qi-supplementing formulas); (3) Yang-deficiency constipation with cold and difficulty (needs warm-Yang laxatives). Pattern identification is non-negotiable.

Lifestyle and dietary support: increase dietary fibre (vegetables, fruit, whole grains); ensure adequate hydration (2000ml+ daily — oils in the formula require water to lubricate effectively); moderate daily walking or abdominal massage to stimulate peristalsis; establish regular bowel time habits; avoid prolonged sitting; avoid over-reliance on laxatives (the formula is designed to gradually restore normal bowel function, not serve as a permanent laxative replacement).