Mang Xiao Increases the Volume to Stimulate Gut Movement

Finding A Guiding Herb Makes Easier to Find the Most Efficient Formula (20)

Sodium Sulfate With Na₂SO₄•10H₂O enhancing intestinal osmolality

By Hyunchang Cho, L.Ac., Ph.D ([email protected])

1. Pharmacological Hypothesis of Mang Xiao

Mang Xiao has a strong purgative effect by increasing the water content of the intestinal tract, softening the stools, and expediting the speed of food passing through the intestines.

Mang Xiao is sodium sulfate with Na₂SO₄•10H₂O as its main ingredient. In modern Western medicine, Mang Xiao is categorized as an osmotic laxative, enhancing intestinal osmolality and inhibiting water absorption in the intestinal tract, resulting in purgative effects.

Sodium sulfate and Na₂SO₄•10H₂O are not easily absorbed into the intestinal mucosa and are mostly retained in the tract, increasing intestinal osmolality. It inhibits water absorption in the intestinal tract and increases the water content of the intestines. Undigested food is rapidly transferred from the stomach to the small intestine and later discharged as liquid feces in the colon.

In classical Materia Medica, Mang Xiao was categorized as a Heat Clearing, purgative, moisturizing, and softening herb.

Da Huang stimulates intestinal peristalsis by chemically stimulating the enteric nerve plexus. And Mang Xiao increases the volume of intestinal contents, thereby mechanically stimulating the intestinal tract and leading to purgative effects in the form of liquid feces.

2. Clinical Signs of Mang Xiao

Mang Xiao’s therapeutic effects are similar to Da Huang’s, meaning Mang Xiao can also treat Da Huang’s symptoms of constipation, stomach fullness, and mental discomfort. Mang Xiao is usually used alongside Da Huang to increase its effect.

In Shang Han Lun and Jin Kui Yao Lue, Mang Xiao is seldom used alone without Da Huang. Such exceptions are Chai Hu Jia Mang Xiao Tang, Mu Fang Ji Qu Shi Gao Jia Ling Xiao Tang, and Xiao Shi Fan Shi Tang. This is why understanding Mang Xiao’s symptoms (without Da Huang) becomes difficult.

The difference between Mang Xiao and Da Huang is that while Da Huang has selective effects on the lower abdominal cavity, Mang Xiao can affect the chest and upper and lower abdominal cavities as well. This is why Mang Xiao can treat chest bind(結胸), indigestion, and constipation symptoms.

In Shang Han Lun and Jin Kui Yao Lue, we can categorize Mang Xiao formulas by their target areas.

2. Clinical Tips for using Mang Xiao

(1) Main Symptoms: * Without proper daily bowel movement, the level of discomfort caused by constipation, stomach gas and distension would be high.

(2) Possible Symptoms: Indigestion due to overeating (Tao Wei Cheng Qi Tang, Ju Pi Da Huang Po Xiao Tang, or sometimes Tao Ren Cheng Qi Tang)

(3) CAPE: Patients are mostly Excessive Types (obese, well-built, with strong stamina and good appetite).

(4) Tendency: Hard lumps, resistance, and tenderness can be felt in the epigastrium (under the sternum) and lower abdomen. These are just tips that can be taken into consideration in selecting formulas.

(5) Cautions: Like Da Huang, you should be careful with using Mang Xiao for people who are underweight, weak, with low appetite, loose stools or diarrhea, and fatigue and heaviness of the body worsened by diarrhea. But sometimes, in the cases of severe food congestion of Tao Wei Cheng Qi Tang and Ju Pi Da Huang Po Xiao Tang, you can temporarily use Mang Xiao regardless of patients’ CAPE signs.