Traditionally used for
- Digestion
- Bowel health
- Urinary & fluids
- Liver & jaundice
Cautions & contraindications
- Pregnancy
- Young children
- Kidney conditions
- Toxic — professional use only
☯ TCM Properties
Breaks Up Accumulations; Promotes Bowel and Urinary Movement; Clears Heat and Resolves Toxicity; Reduces swelling and dissipates masses; Softens Hardness and Promotes Discharge of Pus; Clears Heat from the Internal Organs
Traditional Chinese Uses
Xiao Shi (potassium nitrate, saltpeter) is a cold, bitter-salty mineral substance used to break down accumulations, stimulate urination and bowel movements, and clear Heat. It appears in classical formulas for jaundice, hard abdominal masses, urinary stones, and toxic swellings. Its potent purgative and dissolving action means it is only used in specific clinical situations by qualified practitioners and is not suitable for self-administration.
Relationships
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Botanical Description
Xiao Shi is the medicinal form of nitre (saltpeter), the naturally crystallizing potassium nitrate (KNO3) that forms as a white efflorescence on damp soils, cave walls, stable floors, and old plastered surfaces in arid regions, where nitrogen-fixing bacteria oxidize organic nitrogen to nitrate that combines with leached potassium. Historically the salt was harvested by leaching nitre-bearing earths with water, evaporating the lye, and recrystallizing the salt as colorless prismatic crystals with a cool sharp taste. Medicinal-grade material is purified by repeated recrystallization and may be roasted to remove water of crystallization. In traditional Chinese medicine Xiao Shi is bitter, salty, and warm, breaking up accumulations and dispersing masses, draining heat downward through purgation, and used in formulas for severe abdominal masses, jaundice from damp-heat, and obstinate constipation; it is also applied externally for sore throat and mouth ulcers. Because of the oxidizing nature of the salt, internal use is closely regulated by classical dosing.
Active Constituents
Potassium nitrate
Nitrate mineral (niter, saltpetre)Concentration: Dominant phase of the refined drug
A strongly water-soluble oxidising salt. Unlike the sulfate minerals it is grouped with in the draining-downward category, it is fully and rapidly absorbed, so an oral dose becomes a systemic nitrate load rather than an osmotic effect confined to the lumen.
Nitrate anion
Oxyanion and oxidising agentConcentration: About 61.3% of KNO3 by mass
The clinically dangerous half of the molecule. Nitrate-reducing bacteria in the mouth and gut convert a fraction of it to nitrite, and nitrite oxidises haemoglobin iron from the ferrous to the ferric state, producing methaemoglobin that cannot carry oxygen and that shifts the dissociation curve of the remaining normal haemoglobin. Absorbed nitrate is also a substrate for endogenous nitrosation to N-nitroso compounds in the acid stomach.
Potassium cation
Alkali metal cation of the parent saltConcentration: About 38.7% of KNO3 by mass; a 2 g dose carries roughly 0.77 g of potassium, about 20 mmol
A therapeutic dose delivers a potassium load in the range of a prescription potassium supplement, entirely absorbed. In normal renal function this is excreted uneventfully; in chronic kidney disease, or alongside a renin-angiotensin blocker or a potassium-sparing diuretic, it is a route to hyperkalaemia that nobody is monitoring for because the source is not recognised as a potassium salt.
Sodium nitrate and sodium chloride
Accessory soluble saltsConcentration: Variable, source-dependent
Co-occur with potassium nitrate in caliche and nitre-bed material and carry through incomplete recrystallisation. Sodium nitrate behaves toxicologically like the potassium salt in respect of the nitrate anion, so their presence does not reduce the methaemoglobin risk, only the potassium load.
Soil, organic matter and microbial residues
Non-mineral process contaminantsConcentration: Substantial in unrefined leached material; largely removed by recrystallisation
Historically the drug was leached from nitrogenous earth scraped from beneath old buildings, stables and latrines, where bacterial oxidation of animal waste generated the nitrate. Crude material from that route carries the organic and microbial load of its source, which is why the classical texts insist the drug be repeatedly dissolved and recrystallised before use.
Heavy metal contaminants
Trace metal impuritiesConcentration: Grade-dependent; not controlled in fertiliser or pyrotechnic grade material
Refined pharmaceutical potassium nitrate is a clean salt, but the fertiliser, food-curing and pyrotechnic grades that are cheap and freely available are not manufactured to a medicinal specification. The contaminant load is therefore a property of the grade purchased rather than of the mineral.
⚠ Drug Interactions
Sodium nitrite (curing salt, pink salt, Prague powder)
Nitrate has to be bacterially reduced to nitrite before it can oxidise haemoglobin, which limits and delays the effect. Sodium nitrite skips that step entirely and forms methaemoglobin directly, so it is far more acutely toxic gram for gram. Sodium nitrite is a white crystalline salt sold cheaply as a meat cure, is chemically indistinguishable from saltpetre by eye, and has become a common agent of fatal self-poisoning: forensic case series from Europe, South Africa and the United States document a rising trend, with death from methaemoglobinaemia within hours.
Clinical note: Never accept unlabelled white crystals as Xiao Shi, and never source it from a butchery or curing supplier. Cyanosis unresponsive to oxygen, a normal arterial oxygen tension with a low pulse oximetry reading, and chocolate-brown blood after any nitrate or nitrite exposure is methaemoglobinaemia: give methylene blue, and be aware that methylene blue is ineffective and itself haemolytic in G6PD deficiency, where exchange transfusion is the fallback.
Natrii Sulfas (Mang Xiao, Po Xiao) and Natrii Sulfas Exsiccatus (Xuan Ming Fen)
The xiao group has been a source of confusion in the Chinese materia medica since at least Tao Hongjing, and Li Shizhen had to devote a passage of the Ben Cao Gang Mu to separating fire-nitre from water-nitre. They are not interchangeable. Mang Xiao is an osmotic cathartic that is barely absorbed; Xiao Shi is absorbed completely and carries a systemic oxidant and potassium load. Dispensing Xiao Shi where Mang Xiao was written substitutes a methaemoglobin-forming salt for a laxative, at laxative doses.
Clinical note: Insist on unambiguous labelling. The classical distinguishing test still works and takes seconds: a few crystals of potassium nitrate dropped on a flame deflagrate with a violet-tinged flare, sodium sulfate does not burn. A documented case of rapid-onset methaemoglobinaemia in a 14-year-old followed ingestion of a traditional potassium nitrate preparation, with pulse oximetry of 58% against an arterial oxygen tension of 90 mmHg.
ACE inhibitors, angiotensin receptor blockers, potassium-sparing diuretics and potassium supplements
Potassium nitrate is about 39% potassium by mass and is fully absorbed, so a 2 g dose is roughly 20 mmol of potassium, comparable to a prescription potassium chloride supplement. Given alongside drugs that block renal potassium excretion, or in chronic kidney disease, this is an additive load. Nobody screening a patient for hyperkalaemia risk will identify a mineral described as a purgative as the culprit.
Clinical note: Do not prescribe Xiao Shi to patients with chronic kidney disease, hypoaldosteronism, or on a renin-angiotensin blocker, spironolactone, amiloride or a potassium supplement. If it is nevertheless taken, check serum potassium.
Dapsone, primaquine, benzocaine, prilocaine, nitroprusside and other methaemoglobin-forming agents
Each of these generates methaemoglobin by a different route, and the effects add. The reserve is smallest where it matters most: infants under about six months have both a higher gastric pH, which lets nitrate-reducing bacteria colonise the stomach, and lower NADH-cytochrome b5 reductase activity, which is why nitrate exposure produces blue baby syndrome in that age group at doses adults tolerate.
Clinical note: Do not give Xiao Shi to infants, in pregnancy, or to any patient on another oxidant drug, and take a careful drug history first. Congenital methaemoglobinaemia and G6PD deficiency are absolute contraindications.
Organic nitrates (glyceryl trinitrate, isosorbide) and PDE5 inhibitors
Inorganic nitrate feeds the nitrate-nitrite-nitric oxide pathway, and dietary nitrate loads produce a small measurable fall in blood pressure. Whether a therapeutic dose of Xiao Shi adds meaningfully to a glyceryl trinitrate or sildenafil effect has not been studied, and the mechanism is not the same as that of organic nitrates, which release nitric oxide directly. Flagged because the direction of effect is the same, not because a clinical event has been reported.
Clinical note: No action is needed beyond ordinary caution. Do not extrapolate the absolute contraindication between organic nitrates and PDE5 inhibitors to this drug, but ask about symptomatic hypotension if the combination arises.
Sulphur (Liu Huang) and charcoal or other combustible dispensary stock
This is not a pharmacological interaction but it is the reason the drug exists in the historical record. Potassium nitrate is a strong oxidiser, and mixed with sulphur and charcoal it is gunpowder; the formula came out of the Chinese alchemical literature before it reached the military one. A dispensary that stores Xiao Shi loose alongside sulphur, dried plant material and charcoal is storing the three components of a deflagrating mixture, and grinding it in a mortar with an organic reducing agent is a genuine ignition risk.
Clinical note: Store Xiao Shi in a sealed container away from sulphur, charcoal and bulk dried herbs, and never triturate it with an organic or reducing substance. Grind it alone.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| not recommended | Not established — see note | Daily | — | — | No ChP monograph. Potassium nitrate. A strong oxidiser; ingestion causes gastroenteritis and methaemoglobinaemia in quantity. Historically a mineral purgative and a component of external preparations. No pharmacopoeial dose is established. |
Historical Texts
Shen Nong Ben Cao Jing
Han dynasty, compiled c. 200 BCE to 200 CEJin Gui Yao Lue (Zhang Zhongjing)
Eastern Han, c. 200 to 210 CEBen Cao Gang Mu (Li Shizhen)
Ming dynasty, completed 1578, first printed 1596Chinese alchemical (danjing) literature and the Wu Jing Zong Yao
Tang to Northern Song, roughly 7th to 11th century; the Wu Jing Zong Yao compiled 1044References
- Kazmi Salman; Farooqi Humaira; Nawaz Ahmad; Afzal Zubia; Idress Aiman; Yousafzai Mohammad Omar; Khan Muhammad Usman. Rapid-onset methemoglobinemia from traditional-medicine-induced potassium nitrate poisoning: successful treatment with methylene blue—a case report . Journal of Medical Case Reports (2024) [DOI]
- Ward Mary; Jones Rena; Brender Jean; De Kok Theo; Weyer Peter; Nolan Bernard; Villanueva Cristina; Van Breda Simone. Drinking Water Nitrate and Human Health: An Updated Review . International Journal of Environmental Research and Public Health (2018) [DOI]
- Bugelli V.; Tarozzi I.; Manetti Alice Chiara; Stefanelli F.; Di Paolo M.; Chericoni S.. Four cases of sodium nitrite suicidal ingestion: A new trend and a relevant Forensic Pathology and Toxicology challenge . Legal Medicine (2022) [DOI]
- Bachan V R; Hlela M B K M. Rising trends in sodium nitrite suicides: A case series from Cape Town, South Africa . South African Medical Journal (2025) [DOI]
- Dai Min; Wang Ding. Mineral medicines of the East: an analysis of records in historical Chinese and Japanese medical texts . Frontiers in Pharmacology (2025) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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