Wa Leng Zi
StarArca subcrenata Lischke, Arca granosa Linnaeus, Arca inflata Reeve
Traditionally used for
- Cough & breathing
- Digestion
☯ TCM Properties
Resolves Phlegm and transforms stasis; Dissipates Nodules and Softens Hardness; Controls Acidity and Stops Pain; Invigorates Blood and disperses accumulations
Traditional Chinese Uses
Wa Leng Zi (cockle shell, blood clam shell) is a neutral, salty substance used in Chinese medicine to dissolve Phlegm and soften hardened masses from Phlegm accumulation — including goiter, scrofula, and thyroid nodules. In its calcined form, its astringent properties become prominent, making it useful for stopping acid reflux, stomachache from hyperacidity, and certain types of bleeding. Its dual role as a Phlegm-dissolving and astringent substance makes it applicable to a range of conditions depending on its preparation.
Relationships
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Botanical Description
Wa Leng Zi consists of the calcified bivalve shells of several species of ark clams in the family Arcidae, principally Arca subcrenata, Arca granosa (Tegillarca granosa), and Arca inflata, harvested from intertidal mudflats and shallow coastal waters of the western Pacific. The shells are thick, roughly oval to subquadrate, strongly inflated, and externally marked by numerous prominent radial ribs crossed by concentric growth lines, giving them a distinctly ridged, sculptural appearance; the hinge is straight with many small teeth. Externally they are dirty white to grayish or brownish, with remnants of a coarse periostracum, and internally porcellanous white. For medicinal use the shells are cleaned, dried, and calcined, then crushed to a coarse or fine powder consisting primarily of calcium carbonate.
Active Constituents
Calcium carbonate
Inorganic carbonate saltConcentration: over 95% of the shell by mass; present as aragonite in the raw drug and converted to calcite on calcination
This is effectively the whole drug. Its clinical actions of controlling acidity and stopping pain are the actions of an antacid, and its interaction profile is the interaction profile of calcium carbonate. Calcination converts aragonite to the more stable calcite and measurably increases how much calcium carbonate dissolves into the decoction, which is why the calcined form is the one used for hyperacidity.
Shell matrix protein
Protein (organic shell matrix)Concentration: roughly 5% of the raw shell; markedly reduced by calcination
The organic fraction that binds the mineral. It is the main compositional difference between the raw and calcined drug and is largely destroyed by calcination, so any activity attributed to it applies only to the uncalcined shell.
Sodium, strontium and other trace elements
Inorganic trace elementsConcentration: calcium is highest, followed by sodium and strontium; levels of calcium, sodium and phosphorus rise after calcination
Principal component analysis of the inorganic elements distinguishes Arcae concha from the similar shell drug Meretricis/Cyclinae concha, and the authors suggest the differing trace-element profile is what separates their therapeutic emphases. No pharmacological effect has been demonstrated for these elements at the doses supplied by the drug.
⚠ Drug Interactions
Tetracyclines and fluoroquinolones (e.g. doxycycline, ciprofloxacin, levofloxacin)
The drug is over 95% calcium carbonate. Divalent calcium chelates tetracyclines and fluoroquinolones in the gut lumen to form poorly absorbed complexes; this is a well-established, clinically significant interaction for any calcium-containing antacid and applies directly to Concha Arcae, which is dosed in grams.
Clinical note: Separate the herb from the antibiotic by at least 2 hours before or 4 to 6 hours after the dose, or suspend the herb for the antibiotic course.
Levothyroxine
Calcium carbonate binds levothyroxine in the gastrointestinal tract and reduces its absorption; this is a documented cause of rising TSH in patients stabilised on replacement. A gram-dose calcium carbonate herb taken with breakfast sits exactly where levothyroxine is normally taken.
Clinical note: Separate by at least 4 hours. Check TSH about 6 to 8 weeks after starting or stopping the herb in a patient on replacement.
Oral bisphosphonates (e.g. alendronate, risedronate)
Oral bisphosphonates have very low bioavailability and are chelated by calcium; the product labels require dosing with plain water and no calcium-containing product for at least 30 to 60 minutes afterwards. Concha Arcae is a calcium carbonate preparation and falls squarely under that restriction.
Clinical note: Give the bisphosphonate on waking with water and keep the herb to later in the day.
Oral iron salts (e.g. ferrous sulfate)
Calcium reduces the absorption of both haem and non-haem iron, and raising gastric pH further reduces the solubility of ferrous salts. Both mechanisms apply to a gram-dose calcium carbonate shell drug.
Clinical note: Separate iron from the herb by at least 2 hours. This matters most in the patient being treated for iron-deficiency anaemia caused by the upper gastrointestinal bleeding the herb is often prescribed alongside.
Drugs needing gastric acid for absorption (e.g. atazanavir, ketoconazole, itraconazole capsules)
Neutralising gastric acid is the intended action of this drug, and the same acid is required to dissolve weakly basic drugs such as the azole antifungals and atazanavir. Antacid co-administration is a recognised cause of subtherapeutic levels of these agents.
Clinical note: Separate by at least 2 hours, and prefer an alternative acid-suppressing strategy if the patient depends on one of these drugs.
Thiazide diuretics and high-dose vitamin D
Thiazides reduce renal calcium excretion and vitamin D increases calcium absorption. Adding a gram-dose absorbable calcium carbonate on top of either is the classic setting for hypercalcaemia, and prolonged high intake of calcium carbonate with alkali is the recognised cause of milk-alkali (calcium-alkali) syndrome with hypercalcaemia, metabolic alkalosis and renal impairment.
Clinical note: Avoid prolonged high-dose use with thiazides or vitamin D supplements. Check serum calcium and creatinine if the herb is used at antacid doses for more than a few weeks.
Concha Meretricis seu Cyclinae (Hai Ge Ke) and Concha Ostreae (Mu Li) as substituted drugs
Arcae concha and Meretricis/Cyclinae concha are described in the analytical literature as marine shell drugs of similar composition and efficacy that are routinely calcined and used clinically, and their inorganic profiles overlap enough that qualitative identification is difficult once the shells are broken or powdered. Trace-element profiling separates them, but a practitioner receiving powdered material cannot. The therapeutic consequence is modest because the calcium carbonate action is shared, but the traditional indications differ.
Clinical note: Buy the drug as recognisable ribbed valves rather than as powder if the distinction matters to the prescription.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| decoction (pre-decocted) | 9–15 g | Daily | — | — | 中国药典 2020 【用法与用量】9～15g，先煎。 【性味与归经】咸，平。归肺、胃、肝经。 — Chinese Pharmacopoeia 2020, quoted verbatim; route and cautions preserved. Replaces a cleared category-filler value. |
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
Both soften hardness and dissipate phlegm nodules; together they reduce stubborn phlegm accumulations.
Named pairing — Lü Jingshan, Shi Jinmo Dui Yao
Evidence Tier
Moderate evidence · 3 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
0
Other clinical trial
0
Observational / case report
0
In vitro / animal
3
1 verified · 2 unverified
Show 3 studies
- Structural and Compositional Changes in Two Marine Shell Traditional Chinese Medicines: A Comparative Analysis Pre- and Post-Calcination
- Antitumor Effect of a Polypeptide Fraction from Arca subcrenata in Vitro and in Vivo
- Identification and Characterization of a Novel Protein ASP-3 Purified from Arca subcrenata and Its Antitumor Mechanism
Other / unclassified
0
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
Structural and Compositional Changes in Two Marine Shell Traditional Chinese Medicines: A Comparative Analysis Pre- and Post-Calcination
Infrared, X-ray and X-ray fluorescence spectroscopy, thermogravimetry and BCA protein assay applied to Arcae concha and Meretricis/Cyclinae concha from several production regions. Calcium carbonate in the raw shells was aragonite and converted to calcite on calcination; protein content fell markedly; calcium, sodium and strontium were the dominant inorganic elements; and calcium carbonate dissolution into the decoction increased after calcination, which supports the traditional preference for the calcined form. Production region made no significant difference, and the authors conclude that composition alone cannot reliably identify these drugs.
Antitumor Effect of a Polypeptide Fraction from Arca subcrenata in Vitro and in Vivo
A polypeptide fraction P2 inhibited proliferation of seven tumour cell lines, with IC50 of 11.43 micrograms/mL in HeLa and 13.00 micrograms/mL in HT-29 at 48 h, had little cytotoxicity to L-02 normal liver cells, and inhibited H-22 and S-180 tumour growth in mice by up to 46.4% and 60.1%. Important caveat for this record: P2 was extracted from the soft body of the clam, not from Concha Arcae. Wa Leng Zi is the shell, which is over 95% calcium carbonate and contains no such polypeptide fraction, so this study does not support any antitumour claim for the shell drug.
Identification and Characterization of a Novel Protein ASP-3 Purified from Arca subcrenata and Its Antitumor Mechanism
ASP-3, a 179-residue 20.6 kDa protein identified as a sarcoplasmic calcium-binding protein, inhibited HepG2 proliferation with IC50 171.18 plus or minus 18.59 micrograms/mL and interacted directly with VEGFR2, reducing its phosphorylation and blocking VEGF-induced tube formation. That the protein is sarcoplasmic makes its origin explicit: it comes from the clam's muscle, not from the shell. As with the polypeptide work, it is evidence about Arca subcrenata as an organism and not about the drug Concha Arcae.
Historical Texts
Ming Yi Bie Lu
Southern and Northern dynastiesRi Hua Zi Ben Cao
Five DynastiesBen Cao Gang Mu
Ming dynastyReferences
- Wu L, Liu C, Yao T, Shi Y, Shen J, Gao X, Qin K. Structural and Compositional Changes in Two Marine Shell Traditional Chinese Medicines: A Comparative Analysis Pre- and Post-Calcination . Journal of AOAC International (2024) [DOI]
- Song L, Ren S, Yu R, Yan C, Li T, Zhao Y. Purification, Characterization and in vitro Anti-Tumor Activity of Proteins from Arca subcrenata Lischke . Marine Drugs (2008) [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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