Baitouweng Tang, a Famous TCM Formula for Dysentery and Diarrhea

Baitouweng Tang (Pulsatilla Decoction) comes from the Shanghan Lun (Treatise on Cold Damage). The Shanghan Lun mentions Baitouweng Tang in two entries. The first is Article 370: "For hot diarrhea with tenesmus, Baitouweng Tang governs." The second is Article 372: "For diarrhea with a desire to drink water, this is due to heat; Baitouweng Tang governs." Baitouweng Tang's composition is: "Baitouweng (Pulsatilla) 2 liang, Huangbo (Phellodendron) 3 liang, Huanglian (Coptis) 3 liang, Qinpi (Fraxinus Bark) 3 liang." The decocting and taking method: "Take the above four herbs with seven sheng of water, boil down to two sheng, strain, and take one sheng warm. If not cured, take another sheng."

Later generations summarized the formula's indication as the hot diarrhea syndrome—distinguished from the Shao-yin pattern of cold diarrhea—clinically characterized by diarrhea of pus and blood, tenesmus, burning heat in the anus, abdominal pain, fever, thirst, scanty dark urine, a red tongue, yellow greasy coating, and a wiry, slippery rapid pulse. TCM holds that this is caused by the accumulation and stagnation of damp-heat evil, which damages the collaterals of the intestines, impairs the free flow of liver qi, and congests the qi mechanism.

These symptoms are mostly seen in intestinal infectious diseases, especially various forms of bacterial dysentery (such as bacillary dysentery, amebic dysentery, chronic bacillary dysentery, and infantile bacillary dysentery). In addition, Baitouweng Tang can also be used to treat ulcerative colitis, acute gastroenteritis, chronic colitis, amebic enteropathy, trichomonal enteritis, salmonella typhimurium enteritis, radiation enteritis, as well as pneumonia, urinary tract infection, pelvic inflammatory disease, and urinary tract infection in pregnancy.

The four herbs used in Baitouweng Tang—Baitouweng, Huanglian, Huangbo and Qinpi—are all commonly used in clinical treatment of acute diarrhea. Modern pharmacological studies confirm that they all have good antibacterial effects, with good therapeutic effect on a variety of pathogenic bacteria including dysentery bacillus; berberine extracted from Huanglian has even been made into a dedicated anti-diarrheal drug. Besides these, some TCM physicians often add Chunshupi (Tree-of-Heaven Bark) and Jiguanhua (Cockscomb Flower) to enhance the formula's efficacy.

Acute diarrhea caused by dysentery and acute gastroenteritis is most common in summer and autumn, because in this season people generally prefer to eat raw and cold foods such as fruits and melons; uncooked food contains some live pathogens of unknown causes, so acute gastrointestinal illness is easy to contract in this season.

The author has had very good results using this formula to treat diarrhea caused by acute infectious diseases. But using it to treat chronic diarrhea such as ulcerative colitis, the effect is not ideal; sometimes a temporary effect is achieved, but the patient easily relapses.

Some explanation is needed regarding the dosage of this formula. According to the Han dynasty system of weights and measures, one Han liang was about 15g in modern measure, but modern practice does not use such large amounts; here one liang can be converted to 5g. In fact, when Zhang Zhongjing had patients take this formula, he initially had them take only half the amount. In our modern decocting, drinking the first decoction is equivalent to one-third of Zhang Zhongjing's original amount, which is not much different.

TCM treatment of acute diarrhea usually requires only one dose to effect a cure. When Zhang Zhongjing used this formula, he boiled seven sheng of water down to two sheng; the first cup drank was one sheng, and if cured, no more was taken; if not cured, the remaining one sheng was drunk. But when should the remaining one sheng be drunk? Zhang Zhongjing did not say.

In the author's own experience, the doctor must closely observe the patient's response. If the patient no longer has diarrhea after the first dose, no further medication is needed. If the patient still has diarrhea shortly after the first dose but the diarrhea has improved, take the medicine immediately after the next bout of diarrhea, without prescribing a fixed interval.

We need to study the Shanghan Lun flexibly. From the perspective of modern medicine, many of the formulas in the Shanghan Lun are used to treat acute infectious diseases. Acute infectious diseases develop rapidly; the doctor must observe the patient closely and cannot proceed slowly as when treating chronic disease.

In the Guizhi Tang entry of the Shanghan Lun, Zhang Zhongjing set forth the principle for treating acute diseases—"observe through a full day and night." Zhang Zhongjing said: "If the disease is severe, take the medicine day and night and observe through a full day and night; after one dose is finished, if the disease pattern still remains, prepare and take another. If no sweat appears, take up to two or three more doses."

He did not mention this again in other entries, but Guizhi Tang is called the "chief of all formulas"; this principle Zhang Zhongjing stated in Guizhi Tang in fact applies to all kinds of acute disease. This passage shows that, in treating acute disease, Zhang Zhongjing did not use just one dose a day, once in the morning and once in the evening, or morning, noon and evening. Rather, he closely observed the patient's response; if effective but the disease remained, he continued medication without interruption.

What if it is ineffective? Zhang Zhongjing mentioned another principle: "know what adverse course has arisen, and treat according to the pattern." Acute patients' conditions change rapidly; one formula may not solve the problem. If there is no improvement at all after medication and the patient's condition instead worsens, the treatment approach must be changed as quickly as possible, without delay, otherwise the best treatment window is easily missed.

Here I need to add a point that Zhang Zhongjing did not mention. That is, in treating emergencies, if we have used the wrong medicine and find the patient's condition rapidly deteriorating, the best thing a doctor can do before using other medicines is to induce vomiting. Because the side effects of some medicines are relatively severe, if the medicine does not match the pattern, it may worsen the patient's condition; after inducing vomiting, the side effects are much smaller.

In addition, Baitouweng's indications include "desire to drink water," which TCM has always interpreted as caused by heat syndrome. Today we know that after frequent diarrhea, the body is severely dehydrated with electrolyte disturbance, which is why there is thirst. In the past we simply gave patients water, "a little at a time"; today we should consider giving the patient some oral rehydration salts.

Patients treated with Baitouweng Tang sometimes have fever; when using this formula, do not be clever and add antipyretics on your own. Baitouweng Tang and Huanglian Jiedu Tang have very similar effects, and both can reduce fever. The author has used these two formulas to treat acute gastroenteritis on many occasions, and both have very good antipyretic effects. Adding Chaihu (Bupleurum) and other antipyretics would instead worsen the patient's condition. Zhang Zhongjing's formulas are rigorously composed; when using them, do not gild the lily.