Li zhong wan
ren shen 9 bai zhu 9 gan jiang 9 zhi gan cao 9
When there is spontaneous diarrhea and thirst is absent, this belongs to tai yin disease, because there is cold in the store house, one should use a warming treatment. A counter flow cold decoction is appropriate.
The formula Li zhong wan is balanced in such a way as to clear the accumulation of dampness and cold in the store house while preventing excessive dryness. Ensuring that yang ming becomes dry while tai yin remains damp.
Over tai yang coldness qi rules. Over yang ming dryness qi rules. Over shao yang ministerial fire qi rules.
Over tai yin dampness qi rules. Over shao yin heat qi rules. Over jue yin, wind rules.
Li zhong wan restores the balance between yang ming dryness and tai yin dampness. Yang ming and Tai yin work together to take the food qi and transform it into clear qi and turbid qi. The clear qi goes up to the chest which becomes true qi that then circulates in the 100 vessels, while the turbid qi goes down and out.
Yang ming conformation of the dry Metal of the west
Tai yin conformation of the damp Earth of the Center
The yang ming and tai yin represent more than just the balance between dryness and dampness. Together they form the Earth and Metal elements. These two elemental movements of qi represent the uptake and transformation of food qi into true qi. Earth and Metal give birth to the element Water and control Water and Wood.
To properly function Earth and Metal need the warm imperial and ministerial blood in the jue yin and shao yin. If shao yin and jue yin are weak then the yang ming and tai yin will suffer leading to less transformation of true qi which in turn leads to less support for shao yin and jue yin.
Li zhong wan warms and dries excessive dampness while moistening and tonifying.
This is achieved with just four herbs. This is possible because each herb works with another and has multiple qualities.
It uses two pairs of herbs to achieve this harmonizing treatment. Ren shen and zhi gan cao moisten Earth while gan jiang and bai zhu dry and warm Earth.
Both ren shen and zhi gan cao treat shao yin. Zhi gan cao directly nourishes the heart and ren shen tonifies the kidney original qi.
Ren shen and bai zhu are restoring the transforming and transport function of tai yin. Ren shen brings healthy fluids to the spleen and bai zhu clears the pathological fluids out. The ren shen raises the clear qi and the bai zhu transports the pathological fluids downward while warming.
It is not a nourishing formula but a tonifying formula. There are no herbs that nourish blood like dang gui. It tonifies and raises the tai yin and shao yin qi while drying and warming.
The gan jiang tonifies and warms the center while astringing or collecting. This restores the excessive downward movement seen as diarrhea. The astringing or collecting nature of gan jiang is used in the formula si ni tang. The gan jiang keeps the fu zi from being excessively dispersing. It is this action that can stop bleeding due to cold.
You could consider using pao jiang which is more astringing than gan jiang and is considered better at stopping bleeding due to cold.
Adding fu ling would support bai zhu in clearing the dampness out through the urine.
This formula is for treating dampness and not phlegm. Phlegm being thicker needs herbs that transform like ban xia.
Li zhong wan uses the sweet taste and astringing nature to raise the qi back upwards while tonifying. The sweet taste is one that is both tonifiying and moderating. Moderating in the way that it calms movement such as physiological wind. Moderating is also a collecting nature that pulls inward.
Sweet governs moderation and its movement can ascend therefore it can tonify the middle burner.
Ren shen, and zhi gan cao are both considered sweet. The astringing nature is used to collect movement towards the middle. Consider that in the formula xiao chai hu tang contains ren shen and zhi gan cao but in da chai hu tang they are not. In da chai hu tang the yang ming stomach domain is dry and fails to descend so using ren shen and zhi gan cao would hold this descension back.
Bai zhu and gan jiang are both dried which produces an astringing nature. Both the sweet and astriging nature are being used together to stop diarrhea and transform the dampness.
Tai yang
Bai zhu dries dampness on the surface
Yang ming
Bai zhu dries dampness and tonifies the stomach, gan jiang tonifies and warms while drying dampness in the stomach and intestines, zhi gan cao tonifies stomach while moistening
Tai yin
Ren shen tonifies spleen while moistening, bai zhu warms and tonifies spleen while drying dampness, gan jiang tonifies and warms while drying dampness in lung and spleen, zhi gan cao tonifies spleen while moistening
Shao yin
Ren shen tonifies original qi, zhi gan cao nourishes heart blood
Understanding Li zhong wan is understanding the balance between the dryness and dampness and there are an infinite number of modifications.
For example the formula si jun zi tang is based on li zhong wan and more can be read here. http://www.itmonline.org/articles/si_junzi_tang/si_junzi_tang.htm