Calcium Carbonate
| Evidence Level: L4 | Predicted Indications: 10 |
Table of Contents
Calcium Carbonate: From Hypercalcemia/Dyspepsia to Calcium-Alkali Syndrome
One-Sentence Summary
Calcium carbonate is a widely used antacid and calcium supplement, originally linked to dyspepsia, hypercalcemia, nephrocalcinosis and phosphorus metabolism disorders. The TxGNN model's top prediction is calcium-alkali syndrome, but this is a drug-induced harm rather than a treatment opportunity. There are no registered clinical trials and 13 publications, almost all reviews and case reports of toxicity.
Quick Overview
| Item | Content |
|---|---|
| Original Indication | Dyspepsia (antacid use). The Singapore approved-indication text is not available in the data compiled for this report; the knowledge graph lists hypercalcemia disease, nephrocalcinosis, phosphorus metabolism disease and dyspepsia. |
| Predicted New Indication | Calcium-alkali syndrome |
| TxGNN Prediction Score | 93.16% |
| Evidence Level | L4 |
| Singapore Market Status | ✓ Marketed |
| Number of Registrations | 8 |
| Recommended Decision | Hold |
Why is This Prediction Reasonable?
Detailed mechanism of action data is not available. Based on known information, calcium carbonate is a calcium salt that neutralizes gastric acid and binds phosphate in the gut. Its efficacy as an antacid is established.
The high TxGNN score for calcium-alkali syndrome most likely reflects a strong drug-disease association, not a therapeutic one. Calcium-alkali syndrome (hypercalcemia, metabolic alkalosis and renal impairment) is caused by excess intake of calcium carbonate and absorbable alkali. The literature describes harm from the drug. It does not show benefit. This should therefore not be treated as a repurposing opportunity.
Other predictions were also reviewed:
- Gastroduodenitis, peptic ulcer disease, duodenogastric reflux: Acid neutralization is mechanistically plausible, but these largely overlap with the existing antacid use. Modern acid suppression (PPIs, H. pylori eradication) has displaced antacids, and no trials are registered. Gastroduodenitis and peptic ulcer disease are best framed as research questions.
- Hyperlipidemia: Small, older studies suggest a modest cholesterol-lowering effect (for example PMID 1456855), but many involve clofibrate combinations, and the effect is small compared with standard therapy.
- Hypophosphatemia, digitalis poisoning: The mechanism points the wrong way. Calcium carbonate binds phosphate and may worsen hypophosphatemia, and calcium can aggravate arrhythmias in digitalis toxicity.
- Primary bone dysplasia, gout, potassium deficiency: No credible mechanistic link or supporting evidence.
Clinical Trial Evidence
Currently no related clinical trials registered.
Literature Evidence
Selected publications for calcium-alkali syndrome (all describe harm caused by the drug):
| PMID | Year | Type | Journal | Key Findings |
|---|---|---|---|---|
| 23543983 | 2013 | Review | Proc (Baylor Univ Med Cent) | Calcium-alkali syndrome has re-emerged as a common cause of hypercalcemia and alkalosis |
| 33732556 | 2021 | Review | Cureus | Historical and pathophysiological update; linked to high calcium carbonate intake |
| 33178509 | 2020 | Review | Cureus | Calcium-alkali syndrome is the third most common cause of hypercalcemia; thiazide association |
| 26260640 | 2015 | Review | Consult Pharm | Guidance for identifying, monitoring and preventing the syndrome in elderly patients |
| 36712775 | 2022 | Case report | Cureus | Hypercalcemic crisis associated with calcium carbonate (Tums) |
| 38784190 | 2024 | Case report | Obstetric Medicine | Severe hypercalcemia requiring dialysis in early twin pregnancy |
| 33842126 | 2021 | Case report | Cureus | Acute kidney injury from calcium carbonate overuse treated with hemodialysis |
| 41444901 | 2025 | Case report | Ann Gen Psychiatry | Over-the-counter calcium carbonate overdose causing the syndrome in a psychiatric patient |
| 25874082 | 2012 | Case report | Clin Kidney J | Hypercalcemic crisis with thiazide and ACE inhibitor, requiring hemodialysis |
| 32675162 | 2020 | Clinical lesson | Clin Med (London) | Over-the-counter antacids causing hypercalcemia, staghorn calculus and renal impairment |
Singapore Market Information
| Authorization Number | Product Name | Dosage Form | Approved Indication |
|---|---|---|---|
| SIN05820P | OHTA'S ISAN ANTACID POWDER | Powder | Not stated |
| SIN08733P | RENNIE TABLET | Tablet | Not stated |
| SIN14016P | GAVISCON DOUBLE ACTION LIQUID, SUSPENSION | Suspension | Not stated |
| SIN13738P | GAVISCON LIQUID SACHETS | Suspension | Not stated |
| SIN13947P | GAVISCON PEPPERMINT TABLETS | Chewable tablet | Not stated |
Three further single-ingredient registrations (SIN14194P, SIN09494P, SIN16041P) are also valid, for 8 in total.
Safety Considerations
- Key risk (from the literature): Excess intake can cause calcium-alkali syndrome (hypercalcemia, metabolic alkalosis, acute kidney injury), including hypercalcemic crisis requiring dialysis. Risk is higher in elderly patients, in pregnancy, and with concurrent thiazide diuretics or ACE inhibitors. Acid rebound has also been discussed for calcium-based antacids.
- Drug Interactions: 100 interactions were identified. Main ones include:
- Major: Dolutegravir
- Moderate: Doxycycline, alendronic acid, risedronic acid, hydrochlorothiazide, nifedipine, amlodipine, atenolol, acetylsalicylic acid, atazanavir, acalabrutinib, acebutolol, amphetamine, proguanil, atropine
- Minor: Famotidine, ranitidine, hydrocortisone, triamcinolone, alprazolam
Please refer to the package insert for label warnings and contraindications.
Conclusion and Next Steps
Decision: Hold
Rationale: The top-ranked prediction, calcium-alkali syndrome, is an adverse effect of calcium carbonate, not a therapeutic target. No registered trials support any predicted indication. The most plausible candidates (gastroduodenitis, peptic ulcer disease) largely duplicate the existing antacid use.
To proceed, the following is needed:
- Package insert warnings and contraindications from HSA, which are blocking for safety screening
- Mechanism of action data
- If pursuing gastric indications, a defined adjunctive symptomatic use with dose limits and hypercalcemia monitoring guardrails
- Controlled studies, as no trial evidence currently exists for any predicted indication
Disclaimer
This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.