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 may not respond to calcium administration.

   
   
4. 
   

   Calcium stabilizes cardiac cell membranes in hyperkalemic states.

Indications

1. 
   

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

   
   
2. 
   

   Hydrofluoric acid exposure (See Hydrogen Fluoride and Hydrofluoric Acid).

   
   
3. 
   

   Hypotension in the setting of calcium channel antagonist (eg, verapamil) overdose (See Calcium Channel Antagonists).

   
   
4. 
   

   Severe hyperkalemia with cardiac manifestations (relatively contraindicated in the setting of digitalis toxicity; see Item III.B below).

   
   
5. 
   

   Symptomatic hypermagnesemia.

Contraindications

1. 
   

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

   
   
2. 
   

   Although controversial, calcium is relatively contraindicated in the setting of intoxication with cardiac glycosides (may aggravate digitalis-induced ventricular tachydysrhythmias) and should be reserved for life-threatening situations.

   
   
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.

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.

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