Usage
- Calcium is prescribed for the prevention and treatment of hypocalcemia, and for conditions associated with calcium deficiency such as osteoporosis, osteomalacia, rickets, hypoparathyroidism, and latent tetany. It is also used in specific clinical settings like cardiac arrest (though no longer routinely recommended in CPR guidelines) and hyperkalemia. In patients with chronic kidney disease (CKD), calcium-based phosphate binders are used to control hyperphosphatemia. Pregnant women with low calcium intakes might receive supplementation to reduce the risk of pre-eclampsia.
- Pharmacological classification: Mineral supplement, electrolyte replacement.
- Mechanism of Action: Calcium plays a vital role in various physiological processes, including nerve impulse transmission, muscle contraction, blood coagulation, and bone formation. Calcium supplementation aims to restore normal calcium levels and support these functions. It acts as a phosphate binder in CKD.
Alternate Names
- Elemental calcium, Calcium salts (various forms like carbonate, citrate, gluconate, acetate, lactate).
- Brand Names: Numerous brand names exist depending on the specific calcium salt and formulation (e.g., Tums, Caltrate, Os-Cal).
How It Works
- Pharmacodynamics: Calcium exerts its effects by influencing membrane permeability, enzyme activity, and cellular signaling. It plays a crucial role in maintaining cell membrane stability and excitability.
- Pharmacokinetics:
- Absorption: Calcium absorption from the gut varies depending on the calcium salt, individual factors (age, vitamin D status), and presence of food. Calcium carbonate is best absorbed when taken with food. Calcium citrate can be taken with or without food.
- Metabolism: Calcium is not metabolized in the conventional sense. Its homeostasis is regulated by vitamin D, parathyroid hormone (PTH), and calcitonin.
- Elimination: Calcium is excreted primarily through the kidneys, with smaller amounts lost in feces and sweat.
- Mode of Action: Calcium ions interact with various cellular components, including ion channels, membrane receptors, and enzymes, to mediate their physiological effects.
- Receptor Binding/Enzyme Inhibition/Neurotransmitter Modulation: While calcium itself does not bind to specific receptors in the same way as drugs, it modulates the activity of calcium-sensing receptors (CaSR). Calcium is also essential for the release of neurotransmitters at nerve synapses.
Dosage
Standard Dosage
Adults: The recommended dietary allowance (RDA) for adults varies:
- 19-50 years (men and women, including pregnant and lactating): 1000 mg daily.
- 51-70 years (men): 1000 mg daily.
- 51+ years (women): 1200 mg daily.
- 71+ years (men and women): 1200 mg daily.
Supplementation should be adjusted to meet the RDA, considering dietary intake. Maximum tolerable upper intake level (UL) is 2500 mg/day for adults 19-50 and 2000 mg/day for adults over 50.
Children: Pediatric dosing varies with age:
- 0-6 months: 200-210 mg
- 6-12 months: 260-270 mg
- 1-3 years: 500-700 mg
- 4-8 years: 800-1000 mg
- 9-18 years: 1300 mg
Special Cases:
- Elderly Patients: Increased calcium and vitamin D requirements. Aim for 1200 mg/day of calcium.
- Patients with Renal Impairment: Total elemental calcium intake should not exceed 2000 mg/day, including dietary calcium and calcium-based phosphate binders. Lower doses may be needed depending on disease stage.
- Patients with Hepatic Dysfunction: Dose adjustments are usually not necessary. However, monitor calcium levels carefully.
- Patients with Comorbid Conditions: Specific guidelines may apply to conditions such as diabetes, cardiovascular disease, and prostate cancer. Consult relevant guidelines.
Clinical Use Cases
Dosage recommendations for specific clinical situations are best determined on a case-by-case basis by the treating physician, as they depend on the severity of hypocalcemia and the clinical context. Refer to clinical guidelines and resources like Medscape for detailed recommendations in emergency situations.
Dosage Adjustments
Dose adjustments are necessary based on individual patient factors, including renal function, hepatic function, age, and concomitant medications. Monitor calcium levels regularly to guide dosage adjustments.
Side Effects
Common Side Effects
Constipation, bloating, gas.
Rare but Serious Side Effects
Hypercalcemia (high blood calcium), milk-alkali syndrome (rare but serious, can cause kidney damage).
Adverse Drug Reactions (ADR)
Severe hypercalcemia can lead to cardiac arrhythmias, confusion, coma.
Contraindications
- Hypercalcemia, hypercalciuria, severe renal impairment, hypersensitivity to calcium salts.
- Certain conditions require caution, such as sarcoidosis and history of kidney stones.
Drug Interactions
- Thiazide diuretics may increase calcium levels.
- Loop diuretics may decrease calcium levels.
- Calcium can interfere with the absorption of certain medications, such as tetracycline antibiotics, bisphosphonates, quinolone antibiotics, levothyroxine, and iron supplements.
- Food high in oxalates (e.g., spinach, rhubarb) or phytates (e.g., whole grains, legumes) can reduce calcium absorption.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: Likely safe when used in recommended amounts.
- Fetal Risks: No known significant fetal risks associated with calcium intake within recommended limits. Excessive calcium intake during pregnancy could potentially affect fetal bone development, but this is rare.
- Breastfeeding: Calcium is excreted in breast milk, but it is considered safe during breastfeeding at recommended intake levels.
Drug Profile Summary
- Mechanism of Action: Calcium supports nerve and muscle function, blood clotting, and bone formation.
- Side Effects: Constipation, bloating, gas; rarely hypercalcemia.
- Contraindications: Hypercalcemia, hypercalciuria, severe renal impairment.
- Drug Interactions: Thiazide diuretics, loop diuretics, certain antibiotics, levothyroxine, iron.
- Pregnancy & Breastfeeding: Likely safe at recommended doses.
- Dosage: Varies with age and condition. See dosage section.
- Monitoring Parameters: Serum calcium levels, especially in patients with renal impairment.
Popular Combinations
Calcium is often combined with vitamin D to enhance calcium absorption.
Precautions
- General Precautions: Evaluate renal function, particularly in patients with CKD. Monitor calcium levels.
- Specific Populations: Consider age-related adjustments, pregnancy safety guidelines, and renal/hepatic function.
- Lifestyle Considerations: Ensure adequate fluid intake to reduce the risk of kidney stones.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Calcium?
A: The recommended dosage for calcium varies by age and condition. See the detailed dosage section above.
Q2: What are the common side effects of calcium supplements?
A: Common side effects include constipation, bloating, and gas.
Q3: Are there any serious side effects associated with calcium?
A: Rarely, high doses of calcium can cause hypercalcemia, which can lead to serious complications if left untreated.
Q4: How does vitamin D interact with calcium?
A: Vitamin D is essential for calcium absorption. Supplementation with vitamin D is often recommended alongside calcium.
Q5: Can I take calcium if I have kidney disease?
A: Calcium supplementation should be carefully managed in patients with kidney disease due to the risk of hypercalcemia and soft tissue calcification. Calcium-based phosphate binders may be used under close monitoring.
Q6: Is calcium safe during pregnancy and breastfeeding?
A: Calcium is considered safe during pregnancy and breastfeeding when taken within the recommended dosage range.
Q7: What are the signs of hypercalcemia?
A: Signs of hypercalcemia can include nausea, vomiting, constipation, increased thirst, increased urination, muscle weakness, bone pain, confusion, and in severe cases, cardiac arrhythmias.
Q8: How can I maximize calcium absorption from supplements?
A: Take calcium supplements in divided doses (less than 500 mg at a time) with food. Calcium carbonate is better absorbed when taken with food.
Q9: Are there any drug interactions I should be aware of with calcium?
A: Calcium can interact with several medications, including certain antibiotics (tetracyclines, quinolones), bisphosphonates, levothyroxine, and iron supplements. It’s important to inform your doctor about all medications and supplements you are taking.
Q10: What foods are good sources of calcium?
A: Good food sources of calcium include dairy products (milk, yogurt, cheese), leafy green vegetables (kale, spinach), fortified plant-based milks and tofu, canned sardines and salmon (with bones).
