Usage
Calcium carbonate is prescribed for various medical conditions, including:
- Calcium supplementation: Used to prevent or treat hypocalcemia (low blood calcium levels) in individuals with insufficient dietary calcium intake. This includes conditions like osteoporosis, osteomalacia/rickets, hypoparathyroidism, and latent tetany. It is also used in specific patient populations such as pregnant/lactating/postmenopausal women, patients on medications like phenytoin, phenobarbital or prednisone.
- Antacid: Neutralizes stomach acid, providing relief from heartburn, acid indigestion, sour stomach, and upset stomach related to these conditions.
- Phosphate binder: Used in patients with chronic kidney disease (CKD) to reduce phosphate absorption from the gut, helping manage hyperphosphatemia.
Pharmacological classifications: Calcium supplement, antacid, phosphate binder.
Mechanism of Action: Calcium carbonate acts as a source of elemental calcium to supplement dietary calcium intake. As an antacid, it neutralizes gastric acid by reacting with hydrochloric acid to form calcium chloride, carbon dioxide, and water, increasing gastric pH. As a phosphate binder, it binds phosphate in the small intestine, preventing its absorption and promoting excretion in the feces. It can also chelate with oxalate to inhibit its absorption and prevent renal calculi formation.
Alternate Names
Calcium carbonate is widely known by this name. Brand names include Tums, Caltrate, Os-Cal, Titralac, and many others. There are numerous generic versions available as well.
How It Works
Pharmacodynamics: Calcium is vital for nerve conduction, muscle contraction, bone mineralization, and blood coagulation. Calcium carbonate elevates serum calcium levels, mitigating symptoms of hypocalcemia. As an antacid, it increases gastric pH, reducing the activity of pepsin and relieving symptoms of hyperacidity. It also promotes gastrointestinal motility. As a phosphate binder, it lowers serum phosphate levels.
Pharmacokinetics:
- Absorption: Absorbed in the small intestine, enhanced by vitamin D and an acidic environment. Approximately 20-40% of elemental calcium is absorbed.
- Metabolism: Not significantly metabolized.
- Elimination: Primarily excreted through feces, with some renal excretion.
Mode of Action: Calcium carbonate does not have specific receptor binding or enzyme inhibition properties. It acts directly by supplementing calcium, neutralizing gastric acid, and binding phosphate.
Elimination pathways: Primarily excreted in feces, with minor renal excretion.
Dosage
Standard Dosage
Adults:
- Calcium supplementation: 1000-1200 mg of elemental calcium daily (equivalent to 2500-3000 mg of calcium carbonate) in divided doses with meals. Daily intake, including dietary calcium and supplements, for adults should preferably not exceed 2000mg. Higher intakes do not improve bone strength. Post-menopausal women’s requirements are higher, at 1.2gm.
- Antacid: 500-1500 mg as needed for symptoms, not exceeding 7000-7500 mg/day for up to 2 weeks.
- Phosphate binder: 1.5-3 grams/day, adjusted based on serum phosphate levels.
Children:
- Dosing is weight-based, usually 45-60 mg/kg/day of elemental calcium, divided into multiple doses.
- Safety and efficacy have not been established in children younger than 2 years.
- Pediatric use should be supervised by a healthcare provider.
Special Cases:
- Elderly Patients: Similar to adult dosing, but monitor closely for side effects and potential drug interactions.
- Patients with Renal Impairment: Dose adjustment is needed if creatinine clearance is <25 mL/min based on serum calcium levels. Monitor serum calcium, phosphate, parathyroid hormone, and alkaline phosphatase.
- Patients with Hepatic Dysfunction: Dose adjustment is generally not required for Calcium Carbonate, but monitor liver function.
- Patients with Comorbid Conditions: Consider interactions with other medications and underlying conditions.
Clinical Use Cases
Calcium carbonate is not routinely administered for intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations unless there is a specific indication like documented hypocalcemia. Calcium chloride is the preferred route in emergent situations.
Dosage Adjustments
Dose adjustments are necessary for patients with renal impairment based on creatinine clearance and serum calcium levels. It is recommended to monitor serum calcium levels during treatment and adjust accordingly. No dose adjustment is necessary for hepatic impairment.
Side Effects
Common Side Effects:
Constipation, bloating, gas, nausea, belching, dry mouth.
Rare but Serious Side Effects:
Hypercalcemia (high blood calcium levels) with symptoms like nausea, vomiting, abdominal pain, constipation, increased thirst/urination, muscle weakness, confusion, or irregular heartbeat. Milk-alkali syndrome can occur with excessive intake.
Long-Term Effects: Chronic kidney disease can occur if high levels of calcium are absorbed over a long period. Kidney stones can also occur.
Adverse Drug Reactions (ADR): Allergic reactions (rare).
Contraindications
- Hypercalcemia
- Hypercalciuria
- Severe renal failure (unless treated with dialysis)
- Kidney stones
- Hypersensitivity to calcium carbonate
Drug Interactions
- Reduces the absorption of certain antibiotics (tetracyclines, quinolones), bisphosphonates, levothyroxine, and other medications.
- Thiazide diuretics can increase calcium levels.
- Interaction with vitamin D can increase calcium absorption.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: C. It should only be used if the potential benefit outweighs the potential risk to the fetus.
- Breastfeeding: It is excreted in breast milk. Monitor infants for signs of hypercalcemia.
Drug Profile Summary
- Mechanism of Action: Supplements calcium, neutralizes gastric acid, binds phosphate.
- Side Effects: Constipation, bloating, gas, nausea, hypercalcemia (rare).
- Contraindications: Hypercalcemia, kidney stones, severe renal failure.
- Drug Interactions: Reduces absorption of several drugs; thiazides increase calcium levels; vitamin D increases absorption.
- Pregnancy & Breastfeeding: Category C; excreted in breast milk.
- Dosage: See dosage section above.
- Monitoring Parameters: Serum calcium, phosphate, renal function tests.
Popular Combinations
Calcium carbonate is often combined with vitamin D to enhance calcium absorption.
Precautions
- Monitor serum calcium levels periodically, particularly in patients with renal impairment.
- Advise patients to report any signs of hypercalcemia.
- Caution in patients with a history of kidney stones.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Calcium Carbonate?
A: Dosage depends on the indication and patient factors. Refer to the detailed dosage guidelines above.
Q2: What are the common side effects of calcium carbonate?
A: Constipation, bloating, gas, nausea, and belching.
Q3: How does calcium carbonate work as an antacid?
A: It neutralizes stomach acid by reacting with hydrochloric acid.
Q4: Can I take calcium carbonate with other medications?
A: It can interact with several medications. Consult the drug interaction section and inform your doctor about all medications you are taking.
Q5: Is calcium carbonate safe during pregnancy?
A: It’s generally considered safe for use during pregnancy under medical supervision, but it’s categorized as pregnancy category C, meaning that animal studies have shown some adverse effects on the fetus.
Q6: Can calcium carbonate cause kidney stones?
A: It can increase the risk of kidney stones in susceptible individuals. It is essential to maintain adequate hydration and monitor urinary calcium levels.
Q7: How should I take calcium carbonate?
A: Take it orally, preferably with food to enhance absorption and reduce gastrointestinal side effects. Chewable tablets should be chewed thoroughly before swallowing.
Q8: What should I do if I miss a dose of calcium carbonate?
A: Take the missed dose as soon as you remember. If it’s close to the time for your next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose.
Q9: What are the signs of hypercalcemia?
A: Nausea, vomiting, constipation, increased thirst, increased urination, muscle weakness, confusion, and irregular heartbeat.
Please note that this information is current as of February 16, 2025, and is intended for use by qualified medical professionals. Always refer to the latest prescribing information and guidelines.
