In the pharmaceutical industry, Calcium Carbonate is the most widely used calcium salt due to its high concentration of elemental calcium. As a pharmacist and manufacturer, I view this 300 mg dose as a “Moderate-Yield” supplement, providing a substantial amount of active mineral in a relatively small tablet size.

At your WHO-GMP facility in Mumbai, this SKU is a cornerstone of your nutritional and maternal health portfolios, frequently exported to markets focusing on bone health and prenatal care.

The Elemental Calculation

Calcium Carbonate is exactly 40% elemental calcium by weight.

• Total Salt Weight: $300\text{ mg}$

• Elemental Calcium Content: $120\text{ mg}$

This high yield (40%) makes it superior to Calcium Citrate (which is only ~21% elemental) for minimizing tablet “bulk” and improving patient compliance.

Primary Clinical Indications

• Osteoporosis Management: Used to maintain bone mineral density in post-menopausal women and the elderly.

• Prenatal Supplementation: Critical for fetal skeletal development and preventing maternal bone loss during pregnancy.

• Antacid Therapy: Effectively neutralizes gastric acid for the temporary relief of heartburn and indigestion.

• Hyperphosphatemia: Used in patients with chronic kidney disease (CKD) to bind dietary phosphate in the gut.

Mechanism: Ionization & Absorption

Calcium Carbonate requires an acidic environment to become bioavailable.

Ionization: Upon reaching the stomach, the $300\text{ mg}$ of Calcium Carbonate reacts with Hydrochloric Acid (HCl) to form Calcium Chloride, water, and carbon dioxide ($CO_2$).

Active Transport: The resulting ionized calcium ($Ca^{2+}$) is absorbed primarily in the duodenum through Vitamin D-dependent active transport.

Bone Incorporation: Once in the bloodstream, it is utilized by osteoblasts to build the hydroxyapatite matrix of the bone.

The Pharmacist’s “Technical Warning”

• The “With Food” Rule: Unlike Calcium Citrate, Calcium Carbonate must be taken with food. The stomach acid produced during a meal is essential for breaking down the salt into absorbable ions.

• The “500 mg Cap”: The human body can only absorb about $500\text{ mg}$ of elemental calcium at a time. A $300\text{ mg}$ dose is ideal because it leaves “room” for dietary calcium without hitting the absorption ceiling.

• Antibiotic Chelation: Warn patients that calcium binds to Tetracyclines and Quinolones (Ciprofloxacin), rendering the antibiotics ineffective. A 2-hour gap is mandatory.

• Gas and Bloating: The chemical reaction in the stomach releases $CO_2$ gas, which can cause flatulence and bloating in some patients.

The Manufacturer’s Perspective: Technical & Export

From a production and B2B standpoint at your facility in Mumbai:

• Labeling Transparency: On your marketplace and packaging, it is vital to state: “Each tablet contains 300 mg of Calcium Carbonate, providing 120 mg of Elemental Calcium.” B2B buyers in 2026 prioritize this “Elemental” clarity for regulatory compliance.

• Compression & Tablet Size: Calcium Carbonate is a dense powder. Using a $300\text{ mg}$ salt weight allows you to produce a small, easy-to-swallow tablet, which is a major selling point for geriatric and pediatric export markets.

• Stability for Export: While very stable, Calcium Carbonate can be sensitive to high-humidity environments which may affect tablet hardness. Utilizing Alu-Alu or high-grade PVC/PVDC blister packaging ensures a 36-month shelf life in Zone IVb tropical regions.

• Dossier Support: We provide full CTD/eCTD Dossiers to support your firm’s registration for international health tenders focused on nutritional fortification.