"Danpi Tang" (Moutan Decoction) for Treating Gastric and Intestinal Abscess (Intestinal Obstruction) According to Waike Dacheng

In Waike Dacheng (Compendium of External Medicine) there is a formula called Danpi Tang (Moutan Decoction), composed as follows: Cortex Moutan (mudanpi) 1 qian (3 g), Semen Trichosanthis (gualouren) 1 qian (3 g), crushed Semen Persicae (taoren) 2 qian (6 g), Mirabilitum (puxiao) 2 qian (6 g), Radix et Rhizoma Rhei (dahuang) 5 qian (15 g).

This formula is prepared as a decoction. Each time, use 2 cups of water (about 400 ml), first decoct the Cortex Moutan, Semen Trichosanthis, Semen Persicae and Radix et Rhizoma Rhei down to 1 cup (about 200 ml), strain out the dregs, then add the Mirabilitum, bring to a boil over fire, and pour out. Take warm, twice a day. After the first dose, observe for 8 hours: if the bowels have moved within those 8 hours, there is no need to take the second dose. If there has been no bowel movement, take the second dose after 8 hours.

This formula has the actions of purging fire and loosening the bowels, cooling blood and dispelling stasis. It is indicated for accumulation of heat-toxin in the stomach and intestines with blood stasis and qi stagnation, causing gastric or intestinal abscess, abdominal swelling and hard glomus, pain on pressure, a slow and tight pulse, when pus has not yet formed. Judging from these symptoms, what this formula treats is what we today call intestinal obstruction.

Although Danpi Tang takes its name from Cortex Moutan, the most heavily dosed herb in it is Radix et Rhizoma Rhei (dahuang). Dahuang is the foremost purgative in Chinese medicine, and with Mirabilitum as its assistant the purgative action is even stronger. Mirabilitum consists mainly of hydrated sodium sulfate and is a powerful laxative. So the main action of this formula is in fact catharsis. Semen Trichosanthis and Semen Persicae also have a purgative effect, while at the same time invigorating blood; Cortex Moutan has the action of cooling and invigorating blood.

Judging from the properties of the component herbs, the main actions of Danpi Tang are activating blood and resolving stasis and inducing catharsis; it is a rather strong purgative. So this formula can indeed treat incomplete intestinal obstruction, but it must not be used for complete intestinal obstruction caused by a tumor.