What are the efficacy and functions of Gegen Qinlian Decoction?

Ge Gen Qin Lian Tang, also known as Ge Gen Huang Qin Huang Lian Tang, is a traditional Chinese medicine prescription primarily used to relieve exterior symptoms and clear interior heat, treating conditions where exterior symptoms remain unresolved and pathogenic heat has entered the interior. It is commonly used to treat heat-induced diarrhea and dysentery, and is prepared by decocting four herbs: Ge Gen (Pueraria lobata), Huang Qin (Scutellaria baicalensis), Huang Lian (Coptis chinensis), and Gan Cao (Glycyrrhiza uralensis).

This prescription has the effect of resolving exterior symptoms and clearing interior heat, primarily treating conditions with unresolved exterior symptoms and pathogenic heat in the interior, manifested as body heat, foul-smelling diarrhea, distressing heat in the chest and epigastric region, dry mouth and thirst, or dyspnea with sweating, red tongue with yellow fur, etc. Ge Gen is the principal herb in this prescription, sweet, pungent, and cool, entering the spleen and stomach meridians. It can disperse the exterior to dissipate heat and also raise the pure yang qi of the spleen and stomach to stop diarrhea, resolving exterior and harmonizing interior symptoms. Huang Lian and Huang Qin, bitter and cold, serve as minister herbs to clear heat and dry dampness, strengthening the intestines and stopping diarrhea. Gan Cao, sweet and moderate, harmonizes the herbs and moderates their actions, serving as the assistant and messenger herb in this prescription. The combination of these four herbs dispels exterior heat and clears interior heat, treating both exterior and interior symptoms simultaneously, leading to spontaneous recovery from heat-induced diarrhea. Patients should be guided by professional doctors in medication after syndrome differentiation, and those with deficiency-cold diarrhea should avoid using it. The doctor may adjust the dosage based on the specific condition of the patient, such as adding fried Bai Shao to nourish the liver and relieve pain for those with abdominal pain; adding Mu Xiang and Bing Lang to promote qi circulation and relieve tenesmus for those with urgent heat-induced dysentery; adding Ban Xia to descend adverse qi and stop vomiting for those with vomiting; and adding Hawthorn to promote digestion for those with food stagnation.