Blood-Activating and Pain-Relieving Effects of the Papaveraceae Plants Xiatianwu (Decumbent Corydalis) and Yanhusuo (Corydalis Tuber)

Both Xiatianwu and Yanhusuo (also called Yuanhu), plants of the Papaveraceae family, are commonly used analgesics in traditional Chinese medicine (TCM), and their active pain-relieving constituents are alkaloids. The analgesic effect of Xiatianwu and Yanhusuo reaches roughly half that of morphine, but unlike morphine they are not prone to causing addiction, making them ideal substitutes for morphine with some efficacy against mild or moderate pain (including cancer pain). However, both Xiatianwu and Yanhusuo exert anti-platelet-aggregation and anticoagulant effects; they are blood-activating herbs in TCM, so they should be used with caution in patients with bleeding tendency. Laboratory tests showing thrombocytopenia and poor coagulation function mean the patient should not take Xiatianwu or Yanhusuo alone.

The TCM herb Xiatianwu is the tuber of Corydalis decumbens, which is distributed mainly in Henan, Jiangsu, Anhui, Zhejiang, Jiangxi, Fujian, Taiwan, Hubei, Hunan and other regions. Its tubers contain decumbenine, corlumidine, bicuculline, palmatine, bulbocapnine, protopine and various other alkaloids.

Pharmacological experiments have confirmed that the bulbocapnine contained in Xiatianwu can induce so-called "catalepsy" in experimental animals: the animals display stupor, somnolence, muscular rigidity and other anesthesia-like responses, probably as a result of its action on the basal ganglia. Xiatianwu alkaloids increase coronary blood flow; the total alkaloids dilate blood vessels and can lower blood pressure. A solution of Xiatianwu alkaloids clearly excites the isolated uterus of experimental animals and can counteract the smooth-muscle-relaxing effect of adrenaline, producing antispasmodic and analgesic effects.

Both in vitro tests and in vivo administration of Xiatianwu total alkaloids markedly inhibit ADP-induced platelet aggregation in rats and clearly suppress platelet-adhesion thrombosis. This may be one of the mechanisms by which Xiatianwu is effective against cerebral vascular embolism and similar diseases.

For a long time Xiatianwu has been widely used in folk medicine, but the classical TCM materia medica works did not record it; only some regional herbal records include it. For example, Zhejiang Folk Commonly Used Herbs holds that Xiatianwu "moves blood, activates blood, stops bleeding, relieves pain and calms spasms"; the National Collection of Chinese Herbal Medicines states that Xiatianwu "dispels wind-dampness and lowers blood pressure; it treats rheumatic arthritis, lumbar muscle strain, hypertension, and hemiplegia caused by cerebrovascular accident." In Zhejiang, folk practice is to mash fresh Xiatianwu, taking 4–5 large pieces or 8–9 small pieces each time, 1–3 times daily, washed down with rice wine or boiling water, taken continuously for 3–12 months to treat hypertension, brain tumor, and hemiplegia caused by cerebral embolism.

The folk experience of Xiatianwu that I have encountered is mainly its use against cancer pain. Xiatianwu is effective against cancer pain; the dosage can be gradually increased according to the patient's pain level, and should not be large when first used. Because famous TCM materia medica works such as the Bencao Gangmu (Compendium of Materia Medica) did not include Xiatianwu, it has not been well promoted and its use is still not widespread. However, the Zhonghua Bencao (Chinese Materia Medica) does include it, and in recent years Xiatianwu has gradually been promoted as an analgesic among TCM physicians and the general public. Xiatianwu is mostly dug up from early April to early May, when its stems and leaves turn yellow; by summer the above-ground parts of Corydalis decumbens are hard to find, hence the name "Xiatianwu" (literally, "absent in summer").

The Zhonghua Bencao summarizes the functions and indications of Xiatianwu as: dispelling wind and dampness, relaxing the sinews and activating blood, unblocking collaterals to stop pain, and lowering blood pressure. It treats rheumatic arthritis, post-stroke hemiplegia, sciatica, sequelae of infantile paralysis, lumbar muscle strain, traumatic injuries, and hypertension. In recent years it has also been found that Xiatianwu eye drops can relieve ciliary muscle spasm and treat myopia in adolescents.

Xiatianwu may be decocted, usually at 3–15 g when entering a decoction. It may also be ground into powder or made into pills or tablets. Its active constituents, similar to those of Yuanhu, do not dissolve easily in water but dissolve in vinegar and ethanol, so better results are obtained after vinegar processing, when soaked in wine, taken as a powder washed down with warm water, or made into pills or tablets.

Yanhusuo is the tuber of Corydalis yanhusuo; the better-known name for this TCM herb is Yuanhu, and it is also called Yanhuan and Xuanhusuo. Yanhusuo is distributed in Henan, Shaanxi, Jiangsu, Anhui, Zhejiang, Hubei and other places; large areas are cultivated in Zhejiang and in Nantong, Jiangsu. Some Yuanhu on the market is adulterated with other Papaveraceae Corydalis plants (such as Corydalis decumbens, Corydalis bulbifera, Corydalis incubis) or with Corydalis remota and Corydalis humilis; these are called fake Yanhusuo. These adulterants also belong to the Papaveraceae family and all have blood-activating and pain-relieving effects.

The tubers of Yanhusuo contain d-corydaline (Yanhusuo jiansu, protopine-like component), dl-tetrahydropalmatine (Yanhusuo yisu), protopine (Yanhusuo bingsu), l-tetrahydrocoptisine (Yanhusuo dingsu), and other alkaloids.

All preparations of Yanhusuo have a clear analgesic effect; pharmacies sell the patent medicine Yuanhu Zhitong Pian (Yuanhu Pain-Relieving Tablets), tablets made from Yanhusuo. The main analgesic active constituents are the various Yanhusuo alkaloids. Its pain-relieving effect is weaker than that of morphine, but Yanhusuo is not addictive, so for patients with mild or moderate pain it is a better choice than morphine. Yanhusuo also has hypnotic, sedative and tranquilizing effects; it can dilate coronary arteries, counteract arrhythmia, and has anti-ulcer and endocrine-regulating actions.

All Papaveraceae plants are slightly toxic, so Xiatianwu and Yanhusuo have some toxicity, though very little. The LD50 of an alcohol extract of Yanhusuo given orally to mice is 100 g/kg, a figure showing that the routine clinical dose of Yuanhu is very safe. The routine dose of Yuanhu in a decoction is 3–10 g, 1.5–3 g when ground into powder and washed down, and even less when made into pills or powders. In my actual clinical experience, the analgesic effect of Yuanhu is best when it is vinegar-processed, ground into a powder, and taken as a powder washed down with warm water.

Because Yuanhu has an antispasmodic effect, traditional TCM holds that it "moves qi." The eight characters that best summarize its actions in traditional TCM are: activating blood and resolving stasis, moving qi and stopping pain. Yuanhu is especially suited to relieving various pain symptoms caused by stasis and spasm. TCM uses it chiefly for chest impediment and cardiac pain, epigastric and abdominal pain, lower back pain, hernia pain, dysmenorrhea, amenorrhea, abdominal masses, postpartum stasis abdominal pain, and traumatic injuries. The Lei Gong Paozhi Lun records: "When cardiac pain threatens to kill, quickly seek Yanhusuo." Yuanhu is indeed very effective for chest impediment, cardiac pain and epigastric pain; stomach pain caused by gastritis and gastric ulcer can both be treated with the patent medicine Yuanhu Zhitong Pian. Stabbing chest pain caused by coronary heart disease can also be treated with Yuanhu Zhitong Pian.

But what I use most is Yuanhu against cancer pain. Yuanhu not only treats cancer pain but also has a certain anti-tumor effect; there are folk cases in which Papaveraceae Corydalis plants or Yanhusuo have successfully treated cancer. For patients with thrombocytopenia, Yuanhu should be used cautiously; when it has to be used, consider combining it with Xianhecao (Agrimonia).

Some doctors may worry that Yuanhu is a blood-activating herb while Xianhecao is a hemostatic herb, and that using them together is inappropriate. My own clinical experience tells me this concern is unnecessary: both Yuanhu and Xianhecao are anti-tumor herbs (Xianhecao's anti-tumor effect is somewhat stronger). Combining them strengthens the anti-tumor effect, while Xianhecao can also counteract the side effects of Yuanhu.

Some patients on anti-tumor targeted therapy see their platelet count drop to dangerously low levels; I use the TCM herb Xianhecao to solve this problem. Practice has shown that after using Xianhecao, the efficacy of the targeted drug (which, like Yuanhu, often has anticoagulant and anti-platelet effects and inhibits tumor angiogenesis) is not only undiminished but enhanced, and the patient's tumor markers fall faster. Thus using blood-activating and hemostatic herbs together does not undermine anti-tumor efficacy.

Yuanhu may be used alone for analgesia or combined with other herbs. TCM rarely treats pain syndromes with a single herb, so Yuanhu is usually one of several analgesics. For stomach pain due to cold stagnation, TCM often combines Yuanhu with warming herbs such as Guizhi (Cinnamon Twig) and Gaoliangjiang (Lesser Galangal), as in "Anzhong San" (Center-Pacifying Powder) from the Heji Jufang. For chest, hypochondriac, epigastric and abdominal pain due to liver-qi stagnation and qi stagnation with blood stasis, it is often combined with Chuanlianzi (Toosendan Fruit), as in Jinlingzi San (here it should be noted that Chuanlianzi has relatively strong side effects and can easily cause liver damage, so it should not be used long-term). For chest impediment and cardiac pain due to heart blood stasis, it is often combined with Danshen (Salvia), Guizhi, Xiebai (Allium Macrostemon) and Gualou (Trichosanthes), decocted with yellow wine or vinegar. For postpartum stasis, amenorrhea and dysmenorrhea, it is often combined with Danggui (Angelica), Puhuang (Typha Pollen) and Chishao (Red Peony), as in Yanhusuo San. For cold hernia abdominal pain and testicular swelling, it is often combined with Juhe (Tangerine Seed), Chuanlianzi and Haizao (Sargassum), as in Juhe Wan (Tangerine Seed Pill). For rheumatic bi pain, it is often combined with Qinjiao (Gentianae Macrophyllae) and Guizhi. Orthopedists often wash down Yuanhu powder with yellow wine to treat traumatic injuries, or use Yuanhu together with Zhizi (Gardenia) for traumatic injuries.

In addition, Yuanhu also has a diuretic effect, making it suitable for patients whose pain is accompanied by difficult urination.