1. Clinical Overview
Calcium (560mg) is a high-dose elemental calcium supplement, typically provided as calcium carbonate (providing ~1400mg of calcium carbonate to yield 560mg of elemental calcium). It is a critical mineral essential for maintaining skeletal integrity, neuromuscular function, cardiac conduction, and blood coagulation. In the Indian context, it is widely used for the prevention and treatment of calcium deficiency, particularly in populations with low dietary intake, postmenopausal women, and the elderly.
| Onset | Duration | Bioavailability |
|---|---|---|
| Absorption begins within 1-2 hours of oral administration, but therapeutic effects on bone mineral density and symptom relief (e.g., muscle cramps) may take weeks to months. | The physiological effects are sustained with regular daily dosing. Serum calcium levels are tightly regulated; excess is excreted or stored in bone. | Approximately 25-35% under optimal conditions (fasting, acidic gastric pH). Bioavailability decreases with food, age, and conditions like achlorhydria. |
2. Mechanism of Action
Calcium is the primary cation for bone mineralization, providing rigidity and strength to the skeletal system. It acts as an intracellular and extracellular messenger in numerous physiological processes. It is essential for excitation-contraction coupling in cardiac and skeletal muscle, excitation-secretion coupling in neurotransmitter and hormone release, and blood coagulation (Factor IV).
3. Indications & Uses
- Prevention and treatment of calcium deficiency
- Osteoporosis prevention and management (adjunct)
- Hypocalcemia (mild to moderate)
- Osteomalacia/Rickets (as an adjunct to Vitamin D)
4. Dosage & Administration
Adult Dosage: 560mg (elemental calcium) once or twice daily, typically with meals. Total daily elemental calcium intake from all sources should not exceed 2000mg.
Administration: Take with or immediately after a meal to enhance absorption and reduce gastric irritation. Swallow tablet whole with a full glass of water. Do not take within 2 hours of iron supplements, tetracyclines, or fluoroquinolones. For optimal absorption, doses >500mg should be split (e.g., twice daily).
5. Side Effects
Common side effects may include:
- Constipation
- Abdominal discomfort or bloating
- Flatulence
- Nausea
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Levothyroxine | Calcium binds to levothyroxine, drastically reducing its absorption. | Major |
| Bisphosphonates (e.g., Alendronate) | Calcium interferes with absorption. Administer at least 2 hours apart. | Major |
| Fluoroquinolones (e.g., Ciprofloxacin) & Tetracyclines | Chelation reduces antibiotic absorption and efficacy. | Major |
| Digoxin | Hypercalcemia potentiates digoxin toxicity, increasing risk of fatal arrhythmias. | Major |
| Thiazide Diuretics | Reduce calcium excretion, increasing risk of hypercalcemia. | Moderate |
| Oral Iron Supplements | Mutual inhibition of absorption. | Moderate |
| Corticosteroids (e.g., Prednisolone) | Reduce calcium absorption and increase excretion. | Moderate |
| Proton Pump Inhibitors (e.g., Omeprazole) | Reduce gastric acid, impairing calcium carbonate dissolution and absorption. | Moderate |
7. Patient Counselling
- DO take with food for better absorption and fewer stomach issues.
- DO drink plenty of fluids throughout the day.
- DO inform your doctor about all other medicines and supplements you take.
- DO NOT take at the same time as iron pills or certain antibiotics (take 2-4 hours apart).
- DO NOT exceed the recommended dose.
8. Toxicology & Storage
Overdose: Acute: Nausea, vomiting, anorexia, constipation, abdominal pain, confusion, polyuria, polydipsia, renal calculi. Severe: Hypercalcemic crisis (stupor, coma, cardiac arrest). Chronic: Milk-alkali syndrome (hypercalcemia, metabolic alkalosis, renal failure).
Storage: Store in a cool, dry place below 30°C. Protect from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.