Ku Shen (Sophora Root)

Chinese Herb Actions

Chinese Herb Dosage

• What is the typical dosage of Ku Shen?

  Roughly 3–15 g decocted internally; up to about 30 g when prepared as an external wash. The root is the part used. Topical washes for skin and genital itching are typically simmered as a stronger, more concentrated decoction and applied externally rather than swallowed.

  Source: cross-referenced against multiple online sources (materia medica consensus); Sacred Lotus sources & references. Reference only — not a prescription.

Chinese Herb Contraindications & Cautions

• Are there cautions for Ku Shen?

  Ku Shen is extremely bitter and cold and readily damages Spleen/Stomach qi — it is contraindicated in cold-type deficiency of the Spleen and Stomach, and is generally avoided in patients with poor appetite, loose stools, or a weak digestion, and used cautiously in pregnancy.

  • Classical incompatibility — Ku Shen is one of the herbs named in the traditional “Eighteen Incompatibilities” (Shi Ba Fan) as antagonistic to Li Lu (Veratrum); the two are not combined in a formula.
  • Not for prolonged, unsupervised use — given its intensity, professional guidance is advised, particularly for internal use over an extended course.

  Note: Some secondary references also pair Ku Shen with additional incompatible herbs beyond Li Lu; only the Li Lu pairing is consistently confirmed across the classical Eighteen Incompatibilities sources we checked, so it is the one documented here with confidence.

  Source: cross-referenced against multiple online sources (materia medica consensus; classical Eighteen Incompatibilities/Shi Ba Fan).

Chinese Herb Toxicity & Overdose

• The decocted root at standard materia medica doses has a long history of safe traditional use, but isolated Sophora flavescens alkaloids (matrine and oxymatrine) have documented dose-dependent toxicity in laboratory studies. Animal and cell research shows matrine can injure liver cells through an oxidative-stress (ROS-dependent) mechanism, and separate metabolomic and transcriptomic studies in rats describe hepatotoxicity from Sophora flavescens alcohol extract and from matrine exposure. This concentrated-alkaloid toxicity is distinct from the traditional decocted-root dose range, but supports the classical caution against overdose or prolonged unsupervised use.

  Sources: PMID 32717422 (matrine-induced mouse liver cell toxicity, ROS-dependent mechanism); PMID 31747812 (Sophora flavescens alcohol extract hepatotoxicity, rat metabolomics); PMID 36440846 (transcriptomic/metabolomic analysis of matrine-induced hepatotoxicity). Preclinical findings; reference note, not a safety guarantee.

Herb-Drug Interactions

• No well-established clinical herb–drug interactions are documented for the decocted root. Because concentrated matrine/oxymatrine preparations (including injectable Compound Kushen Injection, used in China as adjunctive cancer supportive care) are pharmacologically active and hepatically metabolized, practitioner awareness is reasonable for patients also taking hepatotoxic medications — this is precautionary, based on isolated-alkaloid research, not a demonstrated interaction with the crude herb. (Flagged for practitioner confirmation.)

Western / Biomedical Research

Chinese Herb Clinical Studies & Research

Provided as research context — a summary of published biomedical study, not a therapeutic or medical claim.

• Is there modern research on Ku Shen (Sophora flavescens)?

  Yes — but almost all of it concerns the isolated alkaloids matrine and oxymatrine, or injectable extract preparations, not the decocted whole root used in traditional practice. This distinction matters: pharmacology findings for purified matrine/oxymatrine should not be read as findings about drinking a Ku Shen decoction.

  • Isolated-alkaloid pharmacology — a 2020 review describes oxymatrine as having organ- and tissue-protective effects across multiple models via anti-inflammatory, antioxidant, anti-apoptotic, and anti-fibrotic mechanisms, while noting its clinical translation is still developing.
  • Injectable preparation in oncology (China) — Compound Kushen Injection (a matrine/oxymatrine-based injectable, not an oral decoction) has been studied as adjunctive cancer supportive care; a 2023 overview of systematic reviews found the underlying trial quality “extremely low” despite some moderate-certainty findings for lung and digestive cancers, concluding more rigorous evidence is needed.
  • Toxicity side of the same alkaloids — separate research (see Toxicity) documents matrine-induced liver-cell damage in animal/cell models, illustrating that the same isolated compounds studied for therapeutic effect are also studied for dose-dependent harm.

  Overall: promising isolated-compound and injectable-preparation research exists, but it does not directly validate (or invalidate) the traditional decocted root, and clinical evidence quality for the injectable form is still rated low.

  Sources: PMID 31733326 (oxymatrine organ/tissue-protective review); PMID 37328082 (Compound Kushen Injection, overview of systematic reviews in cancer); PMID 32717422 (matrine hepatotoxicity, mouse liver cells). Research context, not a therapeutic claim.

Chinese Herb Notes

• What formulas is Ku Shen combined with?

  Ku Shen appears in formulas built around clearing damp-heat toxin from the skin, most notably Xiao Feng San (“Eliminate Wind Powder”), where it works alongside wind-dispersing and blood-cooling herbs for weeping, itchy skin eruptions such as eczema and urticaria. (Formula context, not treatment advice.)

  How it differs from related bitter-cold, damp-heat herbs:

  • Ku Shen — the strongest emphasis on killing parasites and stopping itching, especially as a topical wash; also promotes urination.
  • Huang Bai — clears damp-heat from the lower burner and drains deficient (empty) heat, with less emphasis on anti-parasitic/anti-itch action.
  • Huang Qin — concentrates more on clearing heat from the upper/middle burner (Lung, Gallbladder) than on skin/genital dampness.

  Source: cross-referenced against multiple online sources (materia medica consensus); Sacred Lotus sources & references (formula-herb linkage).

This herb is incompatible with:

• Li Lu (Radix Et Rhizoma Veratri)