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Coptidis Rhizoma (Huanglian, 黄连):
The qi is cold, the taste is bitter. The taste is strong and the qi is thin, belonging to yin containing yang, with an ascending nature. It is non-toxic.
It enters the Hand-Shaoyin Heart Meridian.
Li Dongyuan states: It drains Heart Fire, removes damp-heat in the Spleen and Stomach, treats irritability, nausea, stagnant heat in the Middle Jiao, dizziness with a desire to vomit, and fullness below the heart. It is an essential medicine for these conditions. Zhang Zhongjing uses it in all five formulas of Xiexin Tang (Drain the Epigastrium Decoction) to treat nine types of epigastric fullness.
Wang Haogu states: It drains the fire of the Heart Meridian, treats sudden redness and swelling of the eyes, and various sores; it must be used. Bitter-cold substances primarily address excess Yang, using bitterness to eliminate it. It calms roundworms, resolves cold obstruction (Han Ge), treats deficiency of the Lower Jiao, and consolidates Kidney Qi.
Zhang Yuansu states: Stir-fried with wine, its action ascends; soaked in wine, it travels to the head.
Shennong Bencao Jing states: It governs hot pathogens, eye pain with tearing, brightens the eyes. It treats abdominal pain with borborygmus, dysentery, and swelling and pain in the female genitalia. For cold and heat disorders of the Five Zang organs, chronic diarrhea with pus and blood, it stops polydipsia and great fright, promotes water metabolism and strengthens bones, harmonizes the Stomach and intestines, benefits the Gallbladder, and treats mouth ulcers. Long-term use prevents forgetfulness.
Wang Haogu states: It enters the Hand-Shaoyin Heart Meridian. Bitterness dries dampness, thus entering the Heart, as Fire tends towards dryness. However, draining the Heart actually drains the Spleen, because the Son can cause the Mother to be full; when full, drain the Son. When treating blood disorders, Fangfeng (Saposhnikoviae Radix) acts as the upper guiding herb, Huanglian as the middle guiding herb, and Diyuyu (Sanguisorbae Radix) as the lower guiding herb.
Zhang Yuansu's ancestral prescription prevents variola (smallpox/varioliform eruptions) for life: decoct one mouthful of Huanglian and administer it to the infant before it cries upon birth; this is highly effective. If administered after crying, even if eruptions occur, they will be mild. Ancient formulas regard Huanglian as the best medicine for treating dysentery.
Kou Zongshi states: In treating dysentery with slight bleeding, one should not rigidly rely on Huanglian. As a bitter-drying agent, it often leads to critical distress in deficient patients, but is suitable for excess patients.
Shennong Bencao Jing further states: Longgu (Fossil Bones), Lishi (Calcitum), and Huangqin (Scutellariae Radix) act as its assistants. It is incompatible with Juhua (Chrysanthemi Flos), Yuanhua (Genkwa Flos), Xuanshen (Scrophulariae Radix), and Baixianpi (Dictamni Cortex). It is inhibited by Kuandonghua (Adenophorae Radix). It overcomes Aconitum and resolves the toxicity of Ban Dou (Crotonis Fructus).

Rhei Radix et Rhizoma (Dahuang, 大黄):
The qi is cold. The taste is bitter, extremely cold. The taste is very strong, belonging to Yin, with a descending nature. It is non-toxic.
It enters the Foot-Yangming Stomach Meridian and Hand-Yangming Large Intestine Meridian. Wine-soaked, it enters the Taiyang Bladder Meridian.
Li Dongyuan states: Its nature moves freely and does not stay static; it drains various excess heat obstructions, promotes bowel movements, cleanses heat from the intestines and stomach, and specifically treats constipation.
Wang Haogu states: Cleanses excess heat.
Zhang Yuansu states: When heat pathogens overflow internally, use bitterness to drain them. Wine-soaked, it enters the Taiyang Meridian; wine-washed, it enters the Yangming Meridian; other meridians do not require wine processing.
Shennong Bencao Jing states: It governs subcutaneous blood stasis, blood closure with chills and fever, breaks masses and accumulations, residual fluid retention and old food stagnation, purges the intestines and stomach, pushes out the old and brings forth the new, promotes the passage of water and grain, harmonizes the center to transform food, and pacifies the Five Zang organs. It levels the Stomach and directs Qi downward, eliminates phlegm and excess, clears inter-intestinal binding heat, relieves epigastric and abdominal fullness, treats cold blood closure in women, distension, lower abdominal pain, and various old blood stasis bindings.
Wang Haogu states: Bitter and cold, it is a Yin-within-Yin medicine. It leaks (purges), pushes out the old and brings forth the new, removes filth to pacify the Five Zang organs. This is akin to quelling chaos to achieve peace, hence its name "General". Entering the Foot-Yangming and Hand-Yangming meridians, guided by wine, it reaches the highest peak; like a boat carrying cargo, it floats in the chest; drained by bitterness, its nature is峻猛 (harsh/potent) reaching downwards. Guided by wine, it can travel to the highest parts, just as objects on a peak are beyond human reach and must be shot down with arrows. Therefore, in Taiyang-Yangming and Zhengyang-Yangming Chengqi Tang (Harmonizing the Yang Decoctions), wine-soaked Dahuang is used. Only Shaoyang-Yangming belongs to the lower meridian, so Xiaochengqi Tang (Minor Harmonizing the Yang Decoction) does not use wine-soaked Dahuang. Miscellaneous formulas use either raw or flour-steamed forms, with varying preparations.
Kou Zongshi states: The modifications of previous texts are already detailed. Zhang Zhongjing treats Heart Qi deficiency with hematemesis and epistaxis using Xiexin Tang, which contains Dahuang, Huangqin, and Huanglian. Some ask: Since Heart Qi is deficient, why not use a Heart-tonifying formula, but rather a draining formula? The answer is: If Heart Qi were solely deficient, there would be no hematemesis or epistaxis. Here, pathogenic heat lodges due to Heart Qi deficiency, causing bleeding. Using bitterness to drain the heat simultaneously tonifies the Heart with bitterness, achieving two goals with one move. For those with this syndrome, it is invariably effective, provided one assesses the deficiency or excess.
Shennong Bencao Jing further states: It is incompatible with Ganqi (Gambir Resina).