Calcium Carbonate

Introduction Overview

Generic Name

calcium carbonate

Brand Name

Alka-Mints, Alka-Seltzer Cool Action Heartburn Relief, Alka-Seltzer Extra Strength Heartburn Relief, Calcium Oyster Shell, Cal-Gest, Icar Prenatal Chewable Calcium, Oyster Cal, Oyster Calcium, Oyster Shell, Oyster Shell Calcium, Oyster Shell Calcium 500, Tums, Tums Antacid Naturals, Tums Chewy Bites, Tums Chewy Bites Ultra Strength, Tums Chewy Delights, Tums E-X, Tums Smoothies, Tums Smoothies Extra Strength, Tums Sugar-Free, Tums Ultra, Calci-Chew, Oysco 500, Os-Cal 500, Oyst Cal 500, Nephro Calci, Dicarbosil, Equilet, Chooz, Alkets, Titralac, Oyster Cal 500, Calcitab, Super Calcium, Calcium Concentrate, Caltro, Oyster, Cal Oys, Alkums, Tums 500, Calcarb, Caltrate, Rolaids Sodium Free, Amilac, Calcium Oyster, Oyst Cal, Calcium Liquid Softgel, Mylanta Child, Maalox Quick Dissolve, Maalox Quick Dissolve Maximum Strength, Ultra Mylanta Calci Tabs, Extra Strength Mylanta Calci Tabs, Os-Cal, Surpass, Surpass Extra Strength, Tums Extra Strength, Maalox Quick Dissolve Extra Strength, Maalox Antacid Barrier, Rolaids Soft Chew, Pepto Children's, Maalox Regular Strength, Maalox Children's, Tums Kids, Tums QuikPak, Calci-Mix, Alcalak

Dosage Form

oral suspension (1250 mg/5 mL), oral tablet (1250 mg; 600 mg; 648 mg), oral tablet chewable (1000 mg; 1177 mg; 500 mg; 600 mg; 750 mg; 850 mg)

Drug Class

Antacids, Minerals and electrolytes

Pharmacokinetics

Absorption:
Calcium carbonate is primarily absorbed in the small intestine where it dissociates into calcium ions and carbonate ions. The absorption efficiency varies depending on multiple factors including gastric acidity, presence of food, and individual physiological states. Calcium carbonate requires an acidic environment for optimal absorption, as it reacts with gastric acid to form soluble calcium chloride, enhancing calcium bioavailability. In conditions of achlorhydria or reduced stomach acid, absorption may be significantly diminished. Concurrent intake with food, especially acidic foods or beverages, can improve calcium absorption by providing the necessary acidic milieu. Pharmacokinetic studies reveal that peak serum calcium levels typically occur within 1 to 2 hours post oral administration.

Distribution:
Following absorption, calcium ions distribute predominantly into the extracellular fluid. Approximately 99% of calcium is stored in the skeletal system, contributing to structural integrity and mineral homeostasis. The remaining calcium is present in plasma and soft tissues either bound primarily to plasma proteins (around 40-45%, mainly albumin), complexed with anions like citrate and phosphate, or as free ionized calcium, which is the physiologically active form. The distribution equilibrium between bound and free calcium is tightly regulated and influenced by serum pH levels. Any variations in protein binding can impact the total but not necessarily the ionized calcium concentrations.

Metabolism:
Calcium carbonate itself is not metabolized enzymatically but undergoes acid-base and ionic dissociation in the gastrointestinal tract. The carbonate ion reacts with gastric hydrochloric acid to release calcium chloride and carbon dioxide. Metabolic processes downstream concern calcium homeostasis rather than drug metabolism, involving hormonal regulation primarily by parathyroid hormone, calcitonin, and active vitamin D metabolites (1,25-dihydroxyvitamin D). These hormones modulate intestinal absorption efficiency, bone resorption, and renal excretion of calcium.

Elimination:
Calcium excess is primarily excreted via the kidneys. Renal handling of calcium involves glomerular filtration followed by variable reabsorption predominantly in the proximal tubules and thick ascending limb of Henle's loop. The urinary excretion rate reflects the balance of intestinal absorption, bone turnover, and systemic calcium demand. Calcium carbonate, when administered orally in standard doses, does not accumulate but is regulated by homeostatic mechanisms to maintain serum calcium within normal physiological range. Fecal excretion constitutes unabsorbed calcium carbonate. Renal clearance can be influenced by factors such as hydration status, renal function, and concomitant medications affecting calcium reabsorption.

Dosage Forms

Available Dosage Forms:
Calcium carbonate is available in several oral formulations catering to different patient needs and compliance factors. These include oral suspension and tablets in both regular and chewable forms. Specifically, formulations include oral suspension at a concentration of 1250 mg per 5 mL, suitable for patients requiring liquid preparations such as children or those unable to swallow tablets. Tablets are available in various strengths including 1250 mg, 600 mg, and 648 mg to accommodate dosing flexibility. Chewable tablets are offered in strengths of 500 mg, 600 mg, 750 mg, 850 mg, 1000 mg, and 1177 mg, facilitating ease of administration and rapid onset of action especially as an antacid.

Dosages for Adults and Adolescents:
Dosing regimens for calcium carbonate depend on the indication—whether for calcium deficiency treatment or for symptomatic relief of acid indigestion and heartburn. For adults and adolescents, typical daily elemental calcium intake ranges from 1000 mg to 1300 mg, which may require corresponding calcium carbonate doses with consideration of elemental calcium content (calcium carbonate approximately contains 40% elemental calcium). For antacid use, doses can range from 1000 mg to 4000 mg daily, divided into multiple doses taken as needed. In calcium supplementation, doses are tailored based on dietary intake and serum levels, often starting at 500 mg to 1250 mg per dose.

Specific Patient Populations:
Dose adjustments or careful monitoring are necessary in patients with renal impairment, hypercalcemia, or disorders affecting calcium metabolism such as hyperparathyroidism. Pregnant or breastfeeding women should consult healthcare providers for appropriate dosing to maintain adequate calcium nutrition without excessive intake. Pediatric dosing primarily uses liquid suspensions for ease of administration, with doses based on body weight and clinical condition. Elderly patients may require supplementation to prevent osteoporosis but should be monitored for renal function and risk of hypercalcemia. Additionally, patients using concomitant medications that alter calcium absorption or excretion warrant dose modifications to avoid adverse effects or interactions.

Mechanism Of Action

Calcium carbonate acts primarily as a calcium supplement and an antacid. Its antacid effect results from the rapid neutralization of gastric hydrochloric acid by the carbonate ion, producing calcium chloride, water, and carbon dioxide. This reaction elevates gastric pH, thereby reducing acidity and alleviating symptoms of heartburn, acid indigestion, and upset stomach. The rapid onset of action when taken orally makes calcium carbonate effective for symptomatic relief.

As a calcium supplement, calcium carbonate provides an exogenous source of calcium ions necessary for physiological processes including bone mineralization, neuromuscular function, vascular contraction, and intracellular signaling pathways. Calcium ions participate in hydroxyapatite crystal formation within bone, maintaining skeletal strength and density. They also serve as second messengers in signal transduction cascades at the cellular level, influencing muscle contraction and neurotransmitter release.

At the molecular level, calcium carbonate dissociates in acidic conditions to release calcium ions, which are absorbed through the intestinal mucosa. Absorbed calcium influences parathyroid hormone secretion by negative feedback, modulating systemic calcium balance. Compared to other calcium salts, calcium carbonate offers the highest elemental calcium concentration, but requires adequate gastric acid for proper solubilization and absorption.

Clinical studies have demonstrated that calcium carbonate effectively increases serum calcium levels, prevents calcium deficiency, and can reduce bone loss in osteoporosis when used appropriately. Its acid-neutralizing capacity is comparable to or greater than other antacids such as magnesium hydroxide or aluminum hydroxide, although it may produce more CO2 gas leading to potential side effects. Compared with other calcium salts like calcium citrate, calcium carbonate's absorption may be less efficient in patients with achlorhydria or on proton pump inhibitors, necessitating tailored therapeutic choices based on patient-specific factors.

Pharmacological Actions

Neutralizes gastric acid through carbonate ion reaction with hydrochloric acid.
Provides essential calcium ions for physiological functions including bone mineralization.
Acts as a buffering agent to increase gastric pH, reducing symptoms of acid reflux and heartburn.
Supports neuromuscular transmission and cellular signaling by supplying calcium.
Contributes to skeletal maintenance by participating in hydroxyapatite crystal formation.
Reduces phosphate absorption via formation of insoluble calcium phosphate complexes.
May influence parathyroid hormone secretion and calcium homeostasis through systemic calcium levels.
Exerts mild antihyperphosphatemic effects in patients with chronic kidney disease.
Acts as an antacid with rapid onset of action compared to some other alkaline agents.
Possesses a high elemental calcium content facilitating effective supplementation.
Increases intragastric pH providing symptomatic relief for dyspepsia and GERD.
Buffering capacity aids in preventing acid-related mucosal damage in the gastrointestinal tract.
Contributes to correction of hypocalcemia and support during bone growth and repair.

Therapeutic Or Clinical Uses

Prevention and treatment of calcium deficiency including hypocalcemia.
Supplementation in osteoporosis to maintain bone density and reduce fracture risk.
Management of acid indigestion, heartburn, and sour stomach as an over-the-counter antacid.
Adjunctive therapy in patients with parathyroid gland disorders affecting calcium metabolism.
Supportive therapy during pregnancy and lactation to meet increased calcium demands.
Use in chronic kidney disease patients to bind dietary phosphate and reduce hyperphosphatemia.
Treatment of osteopenia by providing supplemental calcium intake.
Relief of symptoms related to gastroesophageal reflux disease (GERD).
As part of comprehensive regimens for metabolic bone disease patients.
Management of hypoparathyroidism-associated hypocalcemia.
Supplementation in pediatric populations with dietary calcium inadequacy.
Prevention of calcium loss in postmenopausal women.
Temporary relief of acid-related gastrointestinal discomfort.
Use in conditions with increased calcium requirements such as rapid growth or fracture healing.
Available as part of combination products for enhanced gastrointestinal symptom control.

Side Or Adverse Effects

Constipation, which may require dietary adjustments or laxatives.
Gastrointestinal upset, including mild nausea and gas formation due to CO2 release.
Hypercalcemia leading to symptoms such as nausea, vomiting, muscle weakness, confusion, and fatigue.
Potential for milk-alkali syndrome when taken in excessive amounts along with high calcium intake.
Less common allergic reactions including hives, rash, or swelling.
Risk of kidney stones particularly in susceptible individuals or those with impaired renal function.
Flatulence resulting from carbon dioxide production in the stomach.
Elevated serum calcium causing disturbances in renal concentrating ability and polyuria.
May cause rebound acid hypersecretion if used excessively as an antacid.
Electrolyte imbalances if taken inappropriately or in overdose conditions.
Rare instances of soft tissue calcification secondary to hypercalcemia.
Possible interference with absorption of certain medications leading to altered efficacy.
Potential for increased blood pressure or edema in predisposed individuals.
Gastric distension or discomfort due to gas build-up.
May exacerbate preexisting renal impairment if overused.

Precautions

Use cautiously in patients with kidney disease or history of kidney stones due to risk of hypercalcemia and nephrolithiasis.
Monitor serum calcium levels in patients receiving long-term supplementation to avoid toxicity.
Adjust dose appropriately during pregnancy and lactation under medical supervision.
Avoid concomitant use with multivitamins or other calcium-containing supplements unless directed by a physician.
Ensure proper timing of administration relative to other medications to avoid absorption interference.
Patients with parathyroid disorders should use only under medical guidance.
Do not exceed recommended dosage to prevent milk-alkali syndrome and related complications.
Use with caution in individuals with gastrointestinal obstruction or impaired motility.
Avoid prolonged use without periodic evaluation of calcium status and renal function.
Not recommended for use in hypocalcemia of critically ill patients needing rapid correction without medical supervision.
Patients with hypercalcemia or hypercalciuria should avoid unnecessary calcium supplementation.
Be aware of potential masking of gastric ulcer symptoms by antacid use.
Pregnant and breastfeeding women should consult healthcare providers before starting therapy.
Careful use advised in patients on digoxin or cardiac glycosides due to risk of arrhythmias associated with hypercalcemia.
Patients with allergy to any component of the formulation should avoid use.

Warnings

Seek immediate medical attention if signs of allergic reaction occur, including hives, difficulty breathing, or swelling of face, lips, tongue, or throat.
High calcium levels may cause serious adverse effects such as nausea, vomiting, muscle weakness, bone pain, confusion, and decreased urine output.
Do not take larger or smaller amounts or use for longer than recommended without consulting a healthcare provider.
Avoid concomitant use with other antacids, multivitamins, or mineral supplements unless advised by doctor.
Use cautiously in individuals with underlying renal impairment or parathyroid disorders.
Discontinue use and consult physician if symptoms of hypercalcemia or unusual fatigue occur.
Keep out of reach of children to prevent accidental overdose which can be life-threatening.
Not intended to diagnose or replace medical evaluation for chronic conditions causing hypocalcemia or acid-related disorders.
Overdose may lead to severe metabolic alkalosis and electrolyte imbalance requiring emergency intervention.
Do not use as a sole therapy for osteoporosis without medical supervision.
Careful monitoring is essential for patients on concurrent medications that interact with calcium.
Prolonged overuse can lead to renal calcification and impairment.
Pregnant women must ensure dosage is appropriate as excessive calcium intake can affect fetal development.
May cause constipation or gastrointestinal obstruction in susceptible patients if taken excessively.
Inform healthcare providers of all medical conditions before starting calcium carbonate therapy.

Contraindication

Known hypersensitivity or allergy to calcium carbonate or any component of the formulation.
Hypercalcemia or hypercalciuria before initiation of therapy.
Patients with diagnosed milk-alkali syndrome or history of this condition.
Severe renal impairment or renal failure without careful medical supervision.
Patients with ventricular fibrillation or cardiac arrhythmias exacerbated by calcium overload.
Use in individuals with undiagnosed abdominal pain or gastrointestinal obstruction contraindicated due to risk of worsening condition.
Not recommended in hypercalcemia induced by malignancy or other pathological states unless under specialist care.
Active kidney stone disease unless supervised by nephrologist or specialist.
Simultaneous use with calcium-containing phosphate binders in patients with elevated serum calcium.
Contraindicated in individuals with metabolic alkalosis due to risk of exacerbation.
Avoid in patients on digoxin without close monitoring due to arrhythmogenic risk.
Patients with parathyroid carcinoma or hyperparathyroidism not controlled by standard therapies.
Contraindicated in idiopathic hypercalciuria unless specifically managed.
Use in children only when specifically prescribed and monitored.
Use cautiously or avoid in patients with hypersensitivity to carbonate or related antacid compounds.

Drug Interactions

May reduce absorption of tetracycline and quinolone antibiotics if taken concurrently, necessitating separation of doses by at least 2 hours.
Calcium can interfere with thyroid hormone (levothyroxine) absorption, requiring careful monitoring and timing of administration.
Concurrent use with bisphosphonates may reduce their bioavailability and therapeutic efficacy.
Interacts with iron salts by decreasing iron absorption, potentially leading to suboptimal treatment of iron deficiency.
Can alter effectiveness of certain antiepileptic drugs by affecting gastrointestinal absorption.
Increased serum calcium from supplementation may potentiate digitalis toxicity, necessitating cardiac monitoring.
Concurrent use with loop or thiazide diuretics affects calcium balance, increasing risk of hypercalcemia or hypocalcemia respectively.
May reduce absorption of phosphates or certain other mineral supplements.
Use with proton pump inhibitors or H2 blockers may diminish calcium carbonate absorption due to reduced gastric acidity.
Magnesium-containing antacids taken with calcium carbonate may increase gastrointestinal side effects.
Vitamin D increases calcium absorption; excessive combined use may risk hypercalcemia.
Calcium carbonate may affect the absorption of certain anticonvulsants and corticosteroids.
Interaction with levodopa/carbidopa can influence their pharmacodynamics requiring dose adjustment.
Multivitamins containing calcium can lead to additive effects and increase risk of adverse events if combined indiscriminately.
Orally administered calcium carbonate can bind and reduce effectiveness of certain herbs or supplements that require acidic environment.

Preparations Of The Drug

Oral suspension containing 1250 mg of calcium carbonate per 5 mL, facilitating dosing flexibility especially in pediatric or dysphagic patients.
Oral tablets in strengths of 1250 mg, 600 mg, and 648 mg designed for standard adult dosing.
Chewable tablets available in various doses: 500 mg, 600 mg, 750 mg, 850 mg, 1000 mg, and 1177 mg to allow titration according to symptom severity or supplementation needs.
Effervescent powder formulations for rapid dissolution and onset of action.
Combination antacid products containing calcium carbonate with magnesium hydroxide or simethicone for enhanced efficacy and reduced gas production.
Prenatal chewable calcium formulations enriched with vitamins and minerals tailored for pregnancy and lactation requirements.
Sugar-free chewable tablets formulated for diabetic or sugar-restricted patients.
Liquid softgel preparations providing alternative administration routes with ease of ingestion.
Multiple branded products offering various flavor options to improve patient compliance.
Buffered formulations aimed at minimizing gastric irritation during prolonged antacid therapy.
Sustained-release formulations in development or limited availability to provide longer duration of calcium supplementation.
Calcium carbonate combined with vitamin D to enhance calcium absorption in some preparations.
Over-the-counter products marketed under numerous brand names for symptomatic relief of dyspepsia and for supplementation.
Prescription-strength calcium carbonate products designed for severe deficiency or clinical indications.
Pediatric formulations with adjusted dosing and palatable flavoring.