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  1. Pharmacology

    1. Calcium is a cation that is necessary for the normal functioning of a variety of enzymes and organ systems, including muscle and nerve tissue. Hypocalcemia, or a blockade of the effects of calcium, may cause muscle cramps, tetany, and ventricular fibrillation. Antagonism of calcium-dependent channels results in hypotension, bradycardia, and atrioventricular (AV) block.

    2. Calcium ions rapidly bind to fluoride ions, abolishing their toxic effects.

    3. Calcium can reverse the negative inotropic effects of calcium antagonists; however, depressed automaticity and AV nodal conduction velocity and vasodilation caused by these agents may not respond to calcium administration.

    4. Calcium stabilizes cardiac cell membranes in hyperkalemic states.

    5. Calcium is a physiologic antagonist to the effects of hypermagnesemia.

  2. Indications

    1. Symptomatic hypocalcemia resulting from intoxication by fluoride, oxalate, or the intravenous anticoagulant citrate.

    2. Hydrofluoric acid exposure.

    3. Hypotension in the setting of calcium channel antagonist (eg, verapamil) toxicity.

    4. Severe hyperkalemia with cardiac manifestations.

    5. Symptomatic hypermagnesemia.

  3. Contraindications

    1. Hypercalcemia except in the setting of calcium channel antagonist poisoning, in which hypercalcemia may be desirable.

    2. Older textbooks list digoxin poisoning as a contraindication, but this warning is not supported by animal studies or human case reports.

    3. Note: Calcium chloride salt should not be used for intradermal, subcutaneous, or intra-arterial injection because it is highly concentrated and may result in further tissue damage. When given intravenously, use a central line or a secure, freely-flowing large peripheral venous line.

  4. Adverse effects

    1. Tissue irritation, particularly with calcium chloride salt; extravasation may cause local irritation or necrosis.

    2. Hypercalcemia, especially in patients with diminished renal function.

    3. Hypotension, bradycardia, syncope, and cardiac dysrhythmias caused by rapid intravenous administration.

    4. Neuromuscular weakness.

    5. Constipation caused by orally administered calcium salts.

    6. Use in pregnancy. FDA Category C (indeterminate). This does not preclude its acute, short-term use for a seriously symptomatic patient (Introduction).

  5. Drug or laboratory interactions

    1. Inotropic and dysrhythmogenic effects of digoxin and other cardiac glycosides may be potentiated by calcium, but this interaction appears largely theoretical, and animal studies have failed to demonstrate harm when calcium is used to treat severe hyperkalemia.

    2. A precipitate will form with solutions containing soluble salts of carbonates, phosphates, or sulfates, and with sodium bicarbonate and various antibiotics.

  6. Dosage and method of administration. Note: A 10% solution of calcium chloride contains three times the amount of calcium ions per milliliter that a 10% solution of calcium gluconate contains. (A 10% solution of calcium chloride contains 27.2 mg/mL of elemental calcium; a 10% solution of calcium gluconate contains 9 mg/mL of elemental calcium.)

    1. Oral fluoride ingestion. Administer calcium-containing antacid (calcium carbonate) orally to complex fluoride ions.

    2. Symptomatic hypocalcemia, hyperkalemia. Give 20–30 mL (2-3 g) of 10% calcium gluconate (children: 0.3-0.4 mL/kg), or 5–10 mL (0.5–1 g) of 10% calcium chloride (children: 0.1-0.2 mL/kg), slowly IV over 5–10 minutes. Repeat as needed every 10–20 minutes.

    3. Calcium antagonist poisoning. May start with doses as described above. Typically, give an initial IV dose of 30 mL (3 g) of 10% calcium gluconate (children: 0.6 ...

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