Calcium Gluconate Injection

General Information

Calcium gluconate is a mineral supplement and medication derived from calcium salt of gluconic acid. Calcium is the most common cation and the fifth most abundant inorganic element in the human body. It is essential for the maintenance of the nervous, muscular, and skeletal systems, and for cell membrane and capillary permeability. Calcium’s role in building bones and supporting their health is well known, but it is also important for nerve conduction, blood coagulation, and electrical conduction in the muscular tissue of the heart.

Generally, calcium salts are used to treat or prevent calcium loss. Calcium is used for the temporary control of irregular heartbeats (arrhythmias), while parenteral calcium is recommended for the treatment of life-threatening cardiac arrhythmias when associated with hyperkalemia, hypermagnesemia, and hypocalcemia. It can also be used in the event of cardiac arrest.

Calcium gluconate is usually not the preferred salt form for treating hypocalcemia, particularly in emergent situations. Usually, calcium gluconate is favored for moderate or mild asymptomatic hypocalcemia due to the lower risk for reactions at the fusion site. Calcium plays an important role in preventing osteoporosis in postmenopausal women. It is not practical as a dietary supplement due to the small concentration of elemental calcium contained in the tablets.

Mechanisms of Action

Calcium plays a crucial role in the function of the nervous, muscular, and skeletal systems, providing structural integrity and support for individual growth. Bone constantly undergoes remodeling and turnover. Mineral release during the process of bone resorption guards hydrogen ions, while the formation of bone produces them. Therefore, bone serves as a calcium repository and as a pool for buffers and electrolytes.

Inhibition of bone resorption is primarily the function of the hormone calcitonin. The control of plasma calcium concentration is maintained by several other hormones, including thyroxine, parathyroid hormone, and calcitriol (1,25-dihydroxycholecalciferol). Calcium is metabolized throughout the body. It assists in heart function, blood coagulation, neuromuscular reactions and more.

Pharmacokinetics

Calcium gluconate can be administered intravenously, orally, or intraosseous.  Calcium is required by tissues throughout the entire body. The majority of calcium (98%) is stored in the bone. Continuous bone remodeling and turnover of the skeletal system release calcium into the systemic circulation on a daily basis.

About 40% of calcium binds to plasma proteins and 10% is in chelated form. Roughly 50% of serum calcium is ionized. The body distributes the nonprotein-bound calcium to protein-poor areas of the body like the cerebrospinal and extracellular fluids. About 80% of calcium is excreted in feces and bile, while urinary excretion accounts for the remaining 20%. The kidneys absorb about 99% of filtered calcium with less than 1% excreted.

Three hormones – calcitonin, parathyroid hormone, and calcitriol – control calcium equilibrium. Androgens, estrogens, insulin, growth hormone, and thyroxine also contribute.

Contraindications/Precautions

Calcium gluconate is contraindicated in patients with ventricular fibrillation and hypercalcemia. 1 Additionally, calcium gluconate should be used with caution in patients with chronic kidney failure due to the increased risk of developing hypercalcemia.

Calcium gluconate injections contain aluminum. When calcium gluconate is used in patients with kidney impairment for an extended period of time, aluminum can reach toxic concentrations. Neonates are especially at risk for aluminum toxicity due to immature kidney function. Research shows that patients with kidney impairment, including newborns, who receive parenteral aluminum at rates greater than 4 to 5 micrograms per day may accumulate excess concentrations of aluminum. High concentrations of aluminum are associated with bone and central nervous system toxicity.

Pregnancy/Breastfeeding

There is little data on the use of calcium gluconate during pregnancy. As such, it is difficult to determine a drug-associated risk of adverse developmental outcomes. However, there is evidence that hypocalcemia can negatively affect both the mother and fetus during pregnancy.

Calcium is a natural component found in human breast milk. Currently, there is no data available regarding the effects of calcium gluconate on calcium concentrations in breast milk. Additionally, there is no data on how calcium gluconate affects milk production or its effects on the breastfed infant.

Interactions

The toxic and inotropic effects of cardiac glycosides and calcium are synergistic. If these drugs are given together (especially when administered intravenously), arrhythmias may occur. In patients receiving cardiac glycosides, intravenous administration of calcium should be avoided; if necessary, it should be given slowly and in small amounts.

Calcium gluconate renders tetracycline antibiotics inactive. As such, patients should never consume these two drugs at the same time orally, nor should they be combined for parenteral administration.

Intravenous solutions containing various drugs are incompatible with calcium gluconate injections. Currently, published data is too limited and/or varied to permit generalization. For more specific information, a specialized reference should be consulted.

Adverse Reactions/Side Effects

The use of calcium gluconate during cardiopulmonary resuscitation is not ideal unless indications exist to offset electrolyte imbalances. Patients with digitalis toxicity should also avoid calcium gluconate, as it presents an increased risk of developing cardiac arrhythmias. Calcium gluconate and cardiac glycosides increase intracellular calcium, which can worsen digitalis toxicity. Therapy to treat cardiac glycosides, however, does not preclude the use of calcium gluconate. Quickly administering a calcium gluconate injection may increase a patient’s risk of serious health problems, including hypotension, cardiac arrhythmias, syncope, vasodilation, and cardiac arrest. To prevent these reactions, it’s important to dilute the calcium gluconate and infuse it slowly. Never give calcium gluconate via intramuscular or subcutaneous administration, as it may result in sloughing or severe necrosis. Providers should also take care to avoid accidental injection or extravasation into the perivascular tissues. If extravasation occurs or manifestations of calcinosis cutis are present, discontinue IV administration promptly and treat as needed. Patients with hyperparathyroidism, vitamin D toxicity, and sarcoidosis may benefit from treatment with calcium gluconate, but use it with caution. All three of these conditions increase the risk of hypercalcemia. Caution should also be used in patients with excess calcium in the urine (hypercalciuria) or kidney stones.