Didang Tang (Wan): A Famous TCM Formula for Activating Blood and Resolving Stasis
This article is organized from the content of a lecture I gave my students yesterday. Because my own level is limited and my work is busy, I have always lectured directly without preparing; so the content inevitably has many inadequate points, and I hope experts will correct me.
This year I am mainly teaching the Shanghan Lun (Treatise on Cold Damage) to my students. The lecture has reached the end of "On the Pulse, Manifestations, and Treatment of Taiyang Disease, Part II"—the bladder blood-storage pattern of the Taiyang channel disease, for which the applicable formula is the famous TCM blood-activating and stasis-resolving formula Didang Tang (Wan). In my lecture I expanded and introduced to students the historical development of the blood-activating and stasis-resolving method among TCM's dispersing methods. So in the end, this class actually became a course introducing TCM's blood-activating and stasis-resolving method.
The original text in the Shanghan Lun regarding Didang Tang and Didang Wan is as follows:
"In Taiyang disease of six or seven days, the exterior pattern still remains, the pulse is faint and deep, yet there is contrary absence of chest-binding; if the person is maniacal, it is because heat is in the lower jiao, the lower abdomen should be rigid and full; if urination is spontaneous, draining blood will cure it. The reason is that, with Taiyang following the channel, stasis-heat is lodged in the interior. Didang Tang governs it.
Didang Tang formula:
Shuizhi (leech) 30 (parched), Mengchong (Tabanus) 30 (parched, wings and legs removed), Taoren (peach kernel) 20 (skin and tip removed), Dahuang (rhubarb) three liang (soaked in wine).
Powder the above four herbs; with five sheng of water, decoct to three sheng, strain. Take one sheng warm; if blood is not discharged, take again.
In Taiyang disease, if the body is yellow, the pulse deep and knotted, the lower abdomen rigid, and urination difficult, there is no blood. If urination is spontaneous and the person is as if mad, the blood pattern is confirmed; Didang Tang governs it.
In cold damage with heat, if the lower abdomen is full, urination should be difficult; now, on the contrary, it is spontaneous—this indicates blood. It should be drained; no other medicine is needed; Didang Wan is appropriate.
Didang Wan formula:
Shuizhi 20, Mengchong 25, Taoren 20, Dahuang three liang.
Pound the above four and divide into four pills. With one sheng of water, boil one pill to seven ge and take. Within one day and night (zuì shí), blood should be discharged; if not, take again.
In Taiyang disease, if urination is spontaneous, because much water was drunk, there will surely be palpitations below the heart. If urination is scant, there will surely be interior urgency."
First, let me translate this passage of medical classical Chinese into vernacular:
Taiyang disease (in TCM's six-channel pattern differentiation, Taiyang disease is disease of the Taiyang channel) has been present for six or seven days, and the exterior pattern still remains. "Exterior pattern still remains" means the patient still has symptoms such as aversion to cold and fever; TCM says that for each bit of aversion to cold, there is a bit of exterior pattern. According to the general outline of Taiyang disease, Taiyang disease should present with "floating pulse, head and neck stiffness and pain, and aversion to cold." So "exterior pattern still remains" here means there is still aversion to cold, head and neck stiffness and pain, and so on.
The pulse should be floating, but the patient's pulse is now "faint and deep," which differs from the typical Taiyang pulse. Why? There may be an omission of text here; the omitted characters should be "the doctor used purgation." Taiyang disease should originally be treated by inducing sweating to release the exterior, but the doctor treated wrongly and used purgation, so the Taiyang disease entered from the exterior into the interior, and the pulse also became deep and faint. Why say so? Because later it says "contrary absence of chest-binding." Generally, Taiyang disease causes chest-binding only after erroneous purgation, so this "contrary absence of chest-binding" reveals that the previous doctor may have wrongly used purgation.
What symptoms does this patient now show? He shows mania. Mania means mental agitation and restlessness. The reason for agitation is that heat originally on the exterior in Taiyang disease has now entered the interior; interior heat produces mental symptoms, which we also saw earlier in Tiaowei Chengqi Tang.
If it enters the interior, it should cause chest-binding; now it directly enters the bladder channel, entering the lower jiao. So besides mania, he has the symptom of "lower abdomen rigid and full." The lower abdomen is the lower belly. If urine accumulates in the bladder, the lower abdomen also becomes rigid and full, but the patient now has "spontaneous urination"—urination is very smooth—so this is not water in the bladder but static blood. So for such a patient, one must "drain blood and cure"; the "blood" drained here means static blood, not normal blood.
The later phrase "The reason is that, with Taiyang following the channel, stasis-heat is lodged in the interior" explains the pathology of this pattern. It means that after Taiyang disease enters the channel, stasis-heat enters the interior—entering the bladder. So later physicians divided Taiyang disease into Taiyang exterior pattern, Taiyang fu-organ pattern, and Taiyang channel pattern; the indication of Didang Tang is the Taiyang fu-organ pattern.
What to do when there is static blood? Use Didang Tang. Why is Didang Tang named "Didang"? Professor Liu Duzhou said that because "didang" is an alias for the leech, and this formula uses leech as the sovereign herb, it is called Didang Tang; this view may be referenced. Other physicians believe Didang Tang is so named because its medicinal nature is fierce.
The several herbs in Didang Tang are all strongly blood-activating and stasis-resolving; among them, Taoren and Dahuang also have purgative action. So many patients, after taking this formula, develop abdominal pain, bloody stool (blood in stool or urine), and diarrhea as side effects.
On this point, the doctor should explain to the patient when prescribing. If not, when these reactions occur the patient will be frightened; this is my personal experience. It is best to tell patients in advance what side effects a certain herb or formula may produce. For one thing, when serious side effects occur they can be handled promptly; for another, when expected side effects occur, the patient will not panic and doubt the doctor and refuse to cooperate.
The doses in this formula are also very large; actually today one does not use such large doses. Today the common dose is "Shuizhi 6 g, Mengchong 6 g, Taoren 9 g, Dahuang 9 g." The dose in the Shanghan Lun was originally also "prepare more, take less." The formula calls for 5 sheng of water, decocted to 3 sheng, but when taking, only one sheng is needed—only one-third of the amount.
The decocting and taking method of this medicine differs from conventional medication. First, Didang Tang requires each herb to be crushed into powder and decocted in the soup. Dahuang, when used to promote bowel movement, should be added later, because the active laxative component of rhubarb is destroyed by prolonged decoction, weakening its purgative effect. In Didang Tang there is no requirement to add later; when rhubarb enters the decoction without being added later, its action is mainly biased toward activating blood and resolving stasis. If in future we prescribe a decoction in which we want rhubarb's blood-activating action rather than its purgative action, note after rhubarb: "do not add later."
Of course, not adding rhubarb later does not mean this formula will not cause diarrhea after being decocted; it still causes diarrhea, just less than when rhubarb is added later. So patients who are especially weak must use this formula with safety in mind.
Also, after taking this medicine once, observe for a day and night—that is, 24 hours. If within that day and night static blood is discharged, no more need be taken; if no static blood is discharged, continue taking. Although Didang Tang above did not specify, Didang Wan later does: "zuì shí" means a day and night.
Here everyone should note: purgative medicines, especially formulas containing rhubarb, should not be taken like ordinary medication. If such a formula is taken 2-3 times a day, it may cause severe diarrhea in the patient; a robust person may survive the diarrhea, but a weak patient may meet with an accident if diarrhea is too much.
If a patient on a rhubarb-containing formula has severe diarrhea, give him cold rice porridge to stop it; cold rice porridge can stop rhubarb-induced diarrhea. Do not let the patient diarrhea too severely, lest it damage righteous qi.
This is like, when sweating method causes too much sweating, the ancients would dust the body with rice powder to stop sweating, just as we now dust the patient with body powder—also to avoid damaging righteous qi. Excessive sweating and excessive purgation both damage the body's righteous qi. Treating disease with sweating, vomiting, and purgation must be done in moderation; sweating should be mild sweating, and purgation should also have measure.
Didang Tang is a very effective formula; if it is a blood-storage pattern, it can be used. Here it is lower-jiao blood storage; actually, for upper-jiao or middle-jiao blood storage, there is also an opportunity to use Didang Tang.
For example, Professor Liu Duzhou used Didang Tang to treat blood stasis at the fundus. King Hui of Chu mistakenly ate food containing leeches and, by accident, cured his own epigastric pain. All this shows that Didang Tang is actually broadly suitable for patterns of binding of stasis and heat.
I myself once saw a professor treat a head-tumor patient with Sanren Tang combined with Didang Tang combined with Shengjiang San, dispelling a tumor that was very swollen on the patient's face.
Didang Tang has many opportunities for use in oncology; Shuizhi (leech), Mengchong (Tabanus), Taoren (peach kernel), and Dahuang (rhubarb) are purgative herbs commonly used in TCM to treat tumors. Some scholars also believe hirudin may have the side effect of promoting hematogenous metastasis of tumors. But actually all blood-activating and stasis-resolving herbs, including the Western drug aspirin, in theory have the side effect of promoting hematogenous metastasis. But some large survey data show that taking aspirin and other blood-activating and stasis-resolving drugs can reduce the recurrence rate of many tumors.
And TCM formulas never contain only one herb (leech); so whether formulas using leech promote hematogenous metastasis in tumor patients is too early to conclude.
It is just that Didang Tang cannot be used for long, because prolonged use damages the patient's righteous qi. Also, for mild blood-storage patterns, avoid Didang Tang if at all possible. Actually, in this passage, Zhang Zhongjing already gave us another approach—the approach of gentle treatment with pills. That is why, after Didang Tang, there is also Didang Wan.
The indication of Didang Wan is very close to that of Didang Tang: lower abdomen full and rigid, spontaneous urination, but without "the person being as if mad." This is also a blood-storage pattern, but this blood-storage pattern is much milder than the Didang Tang pattern. So the dose is reduced.
In Didang Wan, first the amounts of Shuizhi and Mengchong are reduced; then, when decocting, only one-fourth of the amount is decocted, so the dose is much lighter. Pills, whether swallowed whole or prepared by this pill-boiling method—note that in the past, when using pills, there was also this pill-boiling method: boil the pills and take them.
Actually today there are still many patients who cannot swallow pills and can only take liquids; when prescribing pills for such patients, this pill-boiling method can also be used. In the past there was also the powder-boiling method; strictly speaking, Didang Tang and Didang Wan are powder-boiling methods—pound each herb into powder to make a powder, then take the powder and boil it for drinking.
Some later patent medicines, even when made into pills, can also be boiled for drinking. Sometimes in a formula, some herbs are prescribed as decoction pieces and some as pills. In the past, some old doctors would write in a decoction such a prescription as "Liuwei Dihuang Wan two qian, wrapped in cloth and decocted together." This means: boil two qian of Liuwei Dihuang Wan together with the other decoction pieces, so the patient does not have to take so much medicine at once. Some patients have poor stomachs; pills (especially hard water-honey pills) are not easy to digest, so boiling them into soup for the patient to drink is also fine.
Pills have lighter dosage and less damage to righteous qi. So for mild cases, pills can replace decoctions. TCM often says "decoctions are for sweeping; pills are for gentle effect"—decoctions have a cleansing-sweeping action because they are strong; pills take effect slowly. For chronic diseases and weak patients, pills can replace decoctions, achieving results gradually.
There is also the question that blood-activating and stasis-resolving herbs are best taken on an empty stomach early in the day; taken on an empty stomach, they take effect rapidly. Of course, if the disease is in the upper part—for example, lung disease or esophageal disease—taking after meals is more appropriate. Because taken after meals, the medicine does not quickly go down to the lower part, and works better on upper diseases.
After introducing the indications of Didang Tang and Didang Wan, Zhang Zhongjing added a sentence: "In Taiyang disease, if urination is spontaneous, because much water was drunk, there will surely be palpitations below the heart; if urination is scant, there will surely be interior urgency." This is the greatness of the Shanghan Lun. We say the Shanghan Lun pioneered TCM pattern differentiation and treatment, and it is precisely in these details that this shows.
Not only are the clinical presentations of Didang Tang and Didang Wan different, but Zhang Zhongjing also listed another similar situation to distinguish it: the Taiyang-disease patient, after drinking much water, develops the pattern of retained fluid in the stomach. The pattern of retained fluid in the stomach may also present with spontaneous urination and a full, rigid lower abdomen; this must not be mistaken for the Didang Tang or Didang Wan pattern and wrongly treated with Didang Tang or Didang Wan.
For the pattern of retained fluid in the stomach, the patient will "feel palpitations below the heart"—that is, epigastric throbbing and restlessness, even a splashing fluid sound. How to treat it? One must use Poria-series formulas to fortify the spleen, drain water, and transform dampness. This requires, based on the specific clinical symptoms the patient presents, differentiating which decoction pattern the patient belongs to. One can use Fuling Gancao Tang, or Fuling Guizhi Baizhu Gancao Tang, or possibly Wuling San. Which formula specifically to use must follow a principle Zhang Zhongjing stated in the Shanghan Lun: "Know what adverse reversal has occurred; treat according to the pattern."
How to distinguish the retained-stomach-fluid pattern from Didang Tang and Didang Wan patterns? This relies on the doctor taking a very detailed history. One must ask about every detail of the patient very clearly, and see whether the patient's lower-abdominal fullness and rigidity is caused by drinking much water. Zhang Zhongjing saw patients very carefully; his pattern differentiation was meticulous, and the slightest difference in symptoms would change his prescribing strategy. This style of practice is well worth learning; it is the true spirit of evidence-based medicine.
In the preface to the Shanghan Lun, Zhang Zhongjing criticized the sloppy way doctors see patients: "Observe the doctors of today: they do not think to seek the meaning of the classics to extend what they know; each inherits family techniques and from start to finish follows the old. In examining illness and asking about disease, they are only anxious for quick words; facing the patient for a moment, they then prescribe decoctions. Pressing the cun pulse, they do not reach the chi; touching the hand, they do not reach the foot; the three regions—renying, fuyang, and the foot—are not compared. The number of beats of the pulse is not even fifty. They do not know the diagnosis of impending death; the nine indicators are never even glimpsed. The face's mingtang and que-ting are not examined at all. This is what is called seeing the sky through a tube. To wish to distinguish life from death—truly difficult."
Looking at this passage today, many TCM doctors should be covered in shame. Our level may not match Zhang Zhongjing, and the care with which we see patients is far below his, so of course efficacy cannot be guaranteed. If a TCM doctor wants to improve efficacy, the time spent seeing each patient must be sufficient; he must never dismiss a patient in a few hurried minutes. He must very carefully understand the patient's various signs, take a detailed history, pulse, and palpation, find the thread-like symptoms the patient presents, and then, based on what he has learned, judge what pattern the patient has. Only when the pattern is correctly found and the medicine matches the pattern will there be immediate, as-if-answering efficacy.
Didang Tang and Didang Wan are the first dedicated blood-activating and stasis-resolving formulas in the Shanghan Lun. Of course, the Taoren Chengqi Tang discussed earlier also has blood-activating and stasis-resolving action, but that formula is biased toward purgation, so it is named a Chengqi Tang.
Didang Tang and Didang Wan, by contrast, purely treat blood-stasis patterns; Zhang Zhongjing explicitly says "drain blood and cure." This formula can also be called the originator of TCM's blood-activating and stasis-resolving method. But when we study the blood-activating and stasis-resolving method, we cannot stop at Didang Tang and Didang Wan. Zhang Zhongjing's works also include "Xiayuxue Tang" (Blood-Draining Downward Decoction), "Dahuang Zhechong Wan" (Rhubarb and Eupolyphaga Pill), and several other blood-activating and stasis-resolving formulas.
Beyond that, later physicians have also made innovations along the blood-activating and stasis-resolving approach. Here everyone needs to extend their reading to several classic works on blood activation and stasis resolution.
First, the Xian Shou Li Xu Duan Mi Fang (Immortal's Secret Formulas for Treating Injuries and Continuing Fractures), our country's earliest orthopedic and traumatology work. From it we can learn a great deal about blood activation and stasis resolution; especially learn its Siwu Tang (Four-Substance Decoction). This Siwu Tang was originally for treating blood-stasis patterns after fracture; later generations turned it into a famous blood-nourishing formula. That Siwu Tang changed from a blood-activating formula to a blood-nourishing formula also reflects the characteristic of Chinese herbal processing changing medicinal nature. When Siwu Tang is used to activate blood and resolve stasis, Dihuang should be raw Dihuang and Shaoyao should be Chishao. After it became the famous blood-nourishing formula, Dihuang became Shudi (processed Rehmannia) and Shaoyao became Baishao. After processing, Rehmannia changes from a blood-activating herb to a blood-nourishing herb.
Among the modified Siwu Tang formulas there is also Siwu Tang plus Dahuang and Taoren. There is also Siwu Tang modified with Taoren and Honghua; after adding Taoren and Honghua, it is called Taohong Siwu Tang. These are also very classic blood-activating and stasis-resolving formulas with good efficacy for various blood-stasis patterns, but their side effects are far smaller than Didang Tang.
Second, read Wang Qingren's Yilin Gaicuo (Corrections of Errors Among Physicians); the five Zhuyu Tang (Stasis-Expelling Decoctions) created by Wang Qingren are also very classic blood-activating and stasis-resolving formulas.
Third, read Tang Rongchuan's Xuezheng Lun (Treatise on Blood Syndromes); Tang Rongchuan was also a great master of treating blood-stasis patterns, and his Xuezheng Lun has considerable research on various blood-stasis and bleeding syndromes.
Fourth, read Cheng Zhongling's Yixue Xinwu (Medical Mind Enlightenment); study well the indications and contraindications of the dispersing method among the eight methods of medicine. The blood-activating and stasis-resolving method is part of TCM's dispersing method; one must study carefully when the dispersing method is appropriate and when it cannot be used.
This way everyone will have a deeper understanding of the use of the blood-activating and stasis-resolving method. To become a good TCM doctor, one must be broad in knowledge and experience, limited not to one person's works, much less to one formula. In clinical medication, one must choose different formulas according to the severity of the patient's disease and the robustness of his body. Medication must be effective, and even more safe.
Clinically, many blood-stasis patterns can be assaulted with Didang Tang, but afterward one should use gentler formulas like Siwu Tang for follow-up; otherwise it is easy to damage the body's righteous qi.
When we deeply understand the Didang Tang and Didang Wan formulas and grasp the development of the blood-activating and stasis-resolving method, we see the whole picture of TCM's blood-activating and stasis-resolving treatment of disease, and treating disease will be more and more skillful.
Later I lectured on more than ten TCM case records of Didang Tang and Didang Wan treating various diseases; due to space, the case-record lecture is omitted.