Source: Shanghan Lun (Treatise on Exogenous Febrile Diseases).

Ingredients:
No.1  Dahuang (Radix et Rhizoma Rhei) 12 g
No.2  Houpo (Cortex Magnoliae Officinalis) 24 g
No.3  Zhishi (Furctus Aurantii Immaturus) 12 g
No.4  Mangxiao (Natrii Sulphas) 6 g
    
Administration:
No. 2 and No. 3 are to be decocted prior to No. 1 and the decoction is to be taken after removing the residue and infusing No. 4 in it.

Actions:
Drastic purgation for eliminating accumulated heat.

Clinical Application:
This recipe is used to treat excessive-heat syndrome of yangrning-fu organ, manifested as constipation, abdominal pain with tenderness, afternoon fever, thirst with great desire to drink, reddened and prickled tongue with dry yellowish fur or dry blackish fur with fissures, deep and forceful pulse. It is applicable to acute simple ileus, adhesive ileus, acute cholecystitis, acute pancreatitis as well as symptoms of high fever, delirium, coma, convulsion, mania with constipation, yellowish fur and forceful pulse as seen in the course of febrile diseases.

In case of consumption of qi due to excessive heat with lassitude, add Renshen (Radix Ginseng) to replenish qi and prevent exhaustion of qi induced by drastic purgation. If the accumulating heat impairs yin manifesting extreme thirst with great desire to drink, dry reddened tongue with little fur, add Xuanshen (Radix Scrophulariae) and Shengdihuang (Radix Rehmanniae) to nourish yin for the production of body fluid and to moisten dryness for relieving constipation.

Elucidation:
The syndrome results from pathogenic heat accumulating in the large intestine, leading to obstructed flow of fu-qi. This should be treated by eliminating heat to relax the bowels. Ingredient No. 1 acts as monarch drug to eliminate heat and stagnated food and stool in the gastrointestinal tract, and relieve constipation. No. 4 possesses the effect of moistening dryness and softening mass, and is used as minister drug to reinforce the effect of the monarch drug. Both No. 3 and No. 2 are adjuvant drugs, capable of promoting flow of qi and relieving fullness and helping the monarch and minister drugs remove the stagnated food and stool to accelerate discharge of heat and mass.

The four drugs in compatibility generate a drastic efficacy in purging heat and mass. Subtract No. 4 and Xiao Chengqi Tang is formed, which has a mild efficacy. Replace No. 2 and No. 3 with Gancao (Radix Glycyrrhizae), and Tiaowei Chengqi Tang are obtained for laxation of heat and mass. The above three share the name of "San Chengqi Tang" and the selective application of them is made clinically in the light of the degrees of severity.
 
Cautions:
It must be applied with great care to those with excess syndrome of yangming-fu organ but without excessive heat, or those with constitutional deficiency of qi and yin, or the aged, those of general asthenia, or pregnant women.