Herb

Yan Hu Suo (Cu Zhi)

Corydalis tuber (Vinegar processed) | 醋延胡索

Also known as:

Yuan Hu (元胡) , Xuan Hu Suo (玄胡索)

Parts Used

Tuber (块茎 kuài jīng / 块根 kuài gēn)

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

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About This Herb

Traditional Chinese Medicine background and properties

Herb Description

Yán Hú Suǒ (Corydalis) is one of the most important pain-relieving herbs in Chinese medicine. It promotes blood circulation and helps move stagnant Qi, making it widely used for all types of pain, from menstrual cramps and stomach pain to chest pain and pain from injuries. It has been described by classical physicians as the foremost herb for treating pain throughout the entire body.

Herb Category

Main Actions

  • Invigorates Blood and Dispels Stasis
  • Moves Qi
  • Alleviates Pain

How These Actions Work

'Invigorates Blood and moves stasis' means Yán Hú Suǒ promotes blood circulation and helps dissolve areas where blood has become sluggish or stuck. In TCM, when blood fails to flow freely, it causes sharp, fixed, stabbing pain. This herb's warm and pungent nature gives it the ability to open up blood vessels and channels, making it useful for pain caused by blood stasis anywhere in the body, including chest pain, menstrual pain, and pain from traumatic injuries.

'Moves Qi' means this herb helps restore the smooth flow of Qi throughout the body. When Qi becomes stuck (a condition called Qi stagnation), it produces distending, wandering pain, often worsened by emotional stress. Because Yán Hú Suǒ acts on both the Liver channel (which governs the free flow of Qi) and the Spleen channel (which governs digestion), it is particularly effective for pain in the chest, flanks, and abdomen caused by emotional tension or digestive issues.

'Alleviates pain' is the action for which this herb is most celebrated. As Li Shizhen wrote in the Ben Cao Gang Mu, it can "treat all pain throughout the body." Its pain-relieving effect is considered the strongest among common Blood-moving herbs. It works because it simultaneously addresses the two most common causes of pain in TCM: Blood stasis and Qi stagnation. Whether the pain is in the head, chest, abdomen, flanks, or limbs, this herb can be applied. Processing with vinegar (forming Cù Yán Hú Suǒ) significantly enhances its pain-relieving action.

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony that reveal what's out of balance in the body. Yan Hu Suo is traditionally associated with these specific patterns.

The following describes this herb's classification within Traditional Chinese Medicine theory and is provided for educational purposes only.

Why Yan Hu Suo addresses this pattern

Yán Hú Suǒ is warm, pungent, and bitter, entering the Heart and Liver channels. These properties make it ideally suited to address Blood Stasis. Its pungent flavour disperses and moves stagnation, while its warmth activates blood circulation. The Liver stores the Blood and governs its smooth flow, and the Heart governs the blood vessels. By entering both channels, this herb can resolve blood stasis throughout the body, producing its hallmark action of relieving fixed, stabbing pain associated with this pattern.

A practitioner would look for one or more of these signs

Amenorrhea

Menstrual pain with dark, clotted blood

Angina

Chest pain with a fixed, stabbing quality

Trauma

Pain from injuries with visible bruising or swelling

TCM Properties

Temperature

Warm

Taste

Acrid / Pungent (辛 xīn), Bitter (苦 kǔ)

Channels Entered
Heart Liver Spleen
Parts Used

Tuber (块茎 kuài jīng / 块根 kuài gēn)

This is partial information on the herb's TCM properties. More detailed information is available on the herb's dedicated page

Product Details

Manufacturing, supplier, and product specifications

Product Type

Granules

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Botanical & Sourcing

Quality Indicators

Good quality Yan Hu Suo tubers are large (closer to 1.5 cm diameter), plump, and full-bodied, with a firm, hard, and brittle texture. The outer surface should be a clear yellow to yellowish-brown with fine irregular netted wrinkles. The cross-section should be bright yellow with a waxy, horny (角质) luster, indicating thorough boiling during initial processing. The taste should be distinctly bitter, and the smell is faint. Inferior quality tubers are small, greyish-yellow in color, and show a white center on the cross-section (indicating incomplete processing or immature harvest). Avoid pieces that are soft, moldy, or insect-damaged. For vinegar-processed (醋延胡索) slices, the color should be deeper brown-yellow with a slight vinegar aroma.

Primary Growing Regions

The finest quality Yan Hu Suo comes from Zhejiang Province, particularly the Dongyang and Pan'an areas near Jinhua city. This is its recognized terroir region (道地药材), and it is classified as one of the famous "Eight Herbs of Zhejiang" (浙八味). Before the Ming Dynasty, wild Yan Hu Suo was sourced from the border regions of Hebei, Inner Mongolia, and Liaoning. From the Ming Dynasty onward, cultivation shifted to the Jiangsu-Zhejiang area (the Maoshan region of Jiangsu was an early terroir). By the Qing Dynasty, cultivated Zhejiang material became the standard. Hubei, Hunan, Jiangsu, and Shaanxi (especially Chenggu county) also produce commercially available herb, though Zhejiang remains the gold standard.

Harvesting Season

Late spring to early summer (May to June), when the above-ground stems and leaves have withered and died back, signaling that the tubers are fully mature.

Supplier Information

Treasure of the East

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Miscellaneous Info

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Usage & Safety

How to use this herb and important safety information

Important Medical Disclaimer

The information provided here is for educational purposes only and is not intended as medical advice or to replace consultation with a qualified healthcare professional. This herb is a dietary supplement and has not been evaluated by the FDA. It is not intended to diagnose, treat, cure, or prevent any disease.

Always consult with a qualified healthcare provider, particularly if you are pregnant, nursing, have a medical condition, or are taking other medications. Discontinue use and consult your healthcare provider if you experience any adverse reactions.

Recommended Dosage

Instructions for safe storage and consumption

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Traditional Dosage Reference

Standard

3-10g (decoction); 1.5-3g (powder taken directly)

Maximum

Up to 15g in decoction for severe pain conditions under practitioner supervision. For powder (taken directly), do not exceed 3g per dose or 9g daily.

Notes

The standard decoction dose is 3-10g. Taking the herb as ground powder (1.5-3g per dose, swallowed with warm water) is actually more effective for pain relief because the active alkaloids dissolve more readily from powder than through decoction. Vinegar-processed Yan Hu Suo (醋延胡索) is strongly preferred over the raw herb for clinical use, as vinegar processing greatly increases the solubility and bioavailability of the pain-relieving alkaloids. The raw unprocessed herb has poor solubility in water and is rarely used in modern practice. Wine-processed (酒延胡索) is sometimes used when the focus is on moving Blood in the channels and collaterals. For mild Qi stagnation pain, lower doses (3-6g) combined with Qi-moving herbs suffice. For severe Blood stasis pain, higher doses (6-10g) combined with other Blood-moving herbs are used.

Processing Methods

Processing method

The cleaned tubers are soaked or stir-fried with rice vinegar until the vinegar is fully absorbed, then dried. The traditional ratio is approximately 20 jin (10 kg) of vinegar per 100 jin (50 kg) of herb.

How it changes properties

Vinegar processing significantly enhances the pain-relieving action. The acetic acid reacts with the alkaloid bases in the herb to form soluble salts, increasing the bioavailability of key analgesic compounds like tetrahydropalmatine (THP). The thermal nature and channel entry remain unchanged (warm, entering Liver and Spleen). The main clinical change is a marked increase in analgesic potency rather than a shift in thermal nature.

When to use this form

Vinegar-processed Corydalis is the standard clinical form and is preferred over the raw herb in nearly all pain conditions. It is especially favoured for menstrual pain (dysmenorrhea), epigastric and abdominal pain, and chest pain from Blood stasis. The raw form has noticeably weaker analgesic effects and is rarely used in modern practice.

Toxicity Classification

Non-toxic

Yan Hu Suo is classified as non-toxic in the Chinese Pharmacopoeia at standard therapeutic doses. However, it contains over 20 biologically active alkaloids, primarily tetrahydropalmatine (THP/延胡索乙素), protopine, corydaline, and berberine-type alkaloids. At therapeutic oral doses, mild side effects may include dizziness, fatigue, and nausea. When the powdered herb is taken in single doses exceeding 10g, some individuals have experienced skin rash, appetite loss, bloating, abdominal pain, drowsiness, and slowed heart rate with ECG T-wave changes; these effects resolve upon discontinuation. Very large doses or intravenous administration of isolated alkaloids can cause respiratory depression and Parkinson-like tremors. There have been rare case reports of acute hepatitis associated with concentrated tetrahydropalmatine preparations in Western literature. Vinegar processing (醋制) is the standard preparation method, which increases the solubility and bioavailability of the pain-relieving alkaloids while also moderating toxicity compared to crude alcohol extracts.

Contraindications

Avoid

Pregnancy: Yan Hu Suo actively moves Blood and invigorates circulation, which can stimulate uterine contractions and risk miscarriage. Classical sources explicitly prohibit use during pregnancy (孕妇禁服).

Avoid

Active bleeding conditions: Because this herb strongly moves Blood and disperses Blood stasis, it should not be used when there is active hemorrhage, heavy menstrual bleeding without stasis, or bleeding disorders, as it may worsen blood loss.

Caution

Qi and Blood deficiency without stasis: In people who are constitutionally weak or depleted, Yan Hu Suo's moving and dispersing nature can further drain already insufficient Qi and Blood. If pain relief is needed, it should be combined with tonifying herbs.

Caution

Concurrent use of sedative or CNS-depressant medications: The alkaloid tetrahydropalmatine (THP) in Yan Hu Suo has significant sedative and hypnotic effects. Combined use with sedatives, anxiolytics, or opioid analgesics may cause excessive drowsiness or respiratory depression.

Caution

Large doses (over 10g single dose as powder): At high oral doses, individual patients may experience skin rash, poor appetite, bloating, abdominal pain, dizziness, drowsiness, slowed heart rate, and ECG changes (T-wave widening). Very high doses can cause respiratory depression and Parkinsonian-like symptoms.

Caution

Liver disease or impaired hepatic function: There have been case reports of acute hepatitis associated with tetrahydropalmatine-containing preparations. Use with caution in patients with pre-existing liver conditions.

Special Populations

Pregnancy

Contraindicated during pregnancy. Yan Hu Suo is a strongly Blood-moving herb that actively disperses Blood stasis. Its alkaloid components (particularly tetrahydropalmatine) have been shown in animal studies to have effects on smooth muscle, including uterine tissue: small doses can excite the uterus while larger doses inhibit it. Classical sources explicitly state 孕妇禁服 (prohibited for pregnant women). The risk of stimulating uterine contractions and potentially causing miscarriage makes this herb unsafe at any stage of pregnancy.

Breastfeeding

Not recommended during breastfeeding. The alkaloids in Yan Hu Suo, particularly tetrahydropalmatine, are lipophilic compounds that may transfer into breast milk. THP has documented sedative, hypnotic, and dopamine receptor-blocking activity, which could potentially affect a nursing infant's nervous system. There is insufficient safety data on breastfeeding exposure. Additionally, the herb's strong Blood-moving properties may theoretically affect postpartum recovery if not appropriately indicated. Nursing mothers should avoid this herb unless specifically prescribed by a qualified practitioner who can weigh the risks and benefits.

Pediatric Use

Yan Hu Suo is not commonly used in pediatric practice and should be used with caution in children. If prescribed by a qualified practitioner for specific pain conditions in older children, dosages should be significantly reduced (typically one-third to one-half of the adult dose depending on age and weight). The sedative effects of its alkaloids warrant particular caution in young children. Not recommended for infants or toddlers. As with all Blood-moving herbs, it should only be used in children when there is a clear clinical indication of Blood stasis or Qi stagnation causing pain.

Drug Interactions

Sedatives and CNS depressants: Tetrahydropalmatine (THP), the principal active alkaloid in Yan Hu Suo, has well-documented sedative, hypnotic, and anxiolytic properties. It may potentiate the effects of benzodiazepines, barbiturates, opioid analgesics, antihistamines, and other CNS depressants, increasing the risk of excessive sedation, drowsiness, or respiratory depression.

Dopamine-related medications: THP acts as a dopamine receptor antagonist (particularly D1 and D2 receptors). It may interact with dopaminergic drugs including levodopa (used for Parkinson's disease, potentially reducing its efficacy) and antipsychotic medications (potentially adding to dopamine blockade and increasing the risk of extrapyramidal side effects).

Anticoagulant and antiplatelet drugs: Yan Hu Suo has demonstrated anti-platelet aggregation activity in pharmacological studies. Concurrent use with warfarin, heparin, aspirin, clopidogrel, or other anticoagulant/antiplatelet medications may increase bleeding risk. Monitoring is advisable.

Antihypertensive medications: dl-THP has been shown to lower blood pressure and heart rate in animal studies. Combined use with antihypertensive drugs may result in additive hypotensive effects.

Hepatotoxicity considerations: Rare case reports of acute hepatitis have been associated with concentrated THP preparations. Caution is warranted when combining with other potentially hepatotoxic drugs (e.g., acetaminophen, statins, certain antibiotics).

Dietary Advice

When taking Yan Hu Suo for pain due to Blood stasis or Qi stagnation, avoid excessively cold and raw foods (such as iced drinks, raw salads, and cold fruit) as these can constrict circulation and counteract the herb's Blood-moving effects. Foods that gently support circulation, such as warm broths, cooked vegetables, and small amounts of vinegar in cooking, are complementary. Avoid excessive alcohol consumption, as both alcohol and the herb's alkaloids are metabolized by the liver, and the combination may increase sedative effects or hepatic burden.

Cautions & Warnings

Although this herb is typically safe for most individuals, it may cause side effects in some people. Pregnant women, nursing mothers, postpartum women, and those with liver disease should use the formula with caution.

As with any Chinese herbal remedy, it is advisable to seek guidance from a qualified TCM practitioner before beginning treatment.