What is the drug class and mechanism of action (MOA) of calcium?

From the Guidelines

Calcium is classified as an electrolyte and mineral supplement rather than a traditional drug class, with its mechanism of action involving serving as an essential ion that participates in numerous physiological processes throughout the body. Calcium functions by binding to specific proteins to regulate muscle contraction, nerve transmission, blood clotting, and enzyme activity. In the cardiovascular system, calcium enters cardiac and smooth muscle cells through voltage-gated channels to initiate contraction. When used therapeutically as a supplement (commonly as calcium carbonate or calcium citrate), it works by replenishing calcium levels in the body, typically at doses of 1000-1500mg elemental calcium daily for adults, as recommended by the Institute of Medicine 1. For hypocalcemic emergencies, intravenous calcium gluconate (10%) or calcium chloride (10%) may be administered under medical supervision. Calcium's effectiveness depends on vitamin D status, as vitamin D is necessary for intestinal calcium absorption, as noted in a study published in the New England Journal of Medicine 1.

Some key points to consider when prescribing calcium supplements include:

• The amount of elemental calcium provided by different preparations, such as calcium carbonate (40%), calcium citrate (21%), calcium lactate (13%), and calcium gluconate (9%) 1
• The potential for gastrointestinal side effects, such as constipation and bloating, particularly with calcium carbonate, and the recommendation to take it with meals to improve absorption 1
• The importance of considering vitamin D status and ensuring adequate vitamin D levels to optimize calcium absorption, as highlighted in a study published in the British Journal of Sports Medicine 1
• The need to individualize calcium supplementation based on dietary intake, age, and other factors, such as the presence of kidney disease or osteoporosis, as discussed in guidelines published in the American Journal of Kidney Diseases 1

Overall, calcium supplementation is a crucial aspect of preventing and treating conditions like osteoporosis, hypocalcemia, and certain deficiency states, where inadequate calcium levels can lead to bone demineralization, muscle cramping, and neurological symptoms, and should be guided by the most recent and highest-quality evidence, such as the study published in the New England Journal of Medicine in 2013 1.

From the FDA Drug Label

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action Intravenous administration of calcium gluconate increases serum ionized calcium level. Calcium gluconate dissociates into ionized calcium in plasma. Ionized calcium and gluconate are normal constituents of body fluids.

The drug class of calcium is an electrolyte and a mineral supplement. The mechanism of action (MOA) of calcium is to increase serum ionized calcium levels by dissociating into ionized calcium in plasma, which is a normal constituent of body fluids 2. Key points about calcium include:

• It is 100% bioavailable following intravenous injection
• It does not undergo direct metabolism
• It is distributed mainly in the skeleton (99%)
• Only 1% of the total body calcium is distributed within the extracellular fluids and soft tissues
• About 50% of total serum calcium is in the ionized form and represents the biologically active part 2.

From the Research

Drug Class and Mechanism of Action (MOA) of Calcium

• Calcium is classified as a mineral and electrolyte supplement, and its primary mechanism of action is to help maintain strong bones and teeth by promoting calcium deposition in bone tissue 3, 4.
• The absorption of calcium salts depends on their solubility and ionization, with calcium citrate being more easily absorbed than other forms such as calcium lactogluconate and calcium carbonate 3.
• Calcium supplements can help to reduce the incidence of non-vertebral and hip fractures, particularly when combined with vitamin D 3, 4.
• The recommended dosage of calcium supplements varies, but most studies suggest that a daily intake of 1200-1500 mg of elemental calcium is effective in maintaining bone health 3, 5, 6.

Forms of Calcium Supplements

• Calcium supplements come in various forms, including calcium carbonate, calcium citrate, calcium lactate, and calcium gluconate 6.
• Calcium carbonate is the most cost-effective form, but it should be taken with a meal to ensure optimal absorption 6.
• Calcium citrate can be taken without food and is recommended for individuals with achlorhydria or those taking histamine-2 blockers or protein-pump inhibitors 6.

Benefits and Risks of Calcium Supplementation

• Calcium supplementation has been shown to have benefits for bone health, particularly in children, young adults, and menopausal women 6.
• However, recent studies have raised concerns about the potential risks of calcium supplementation, including an increased risk of gastrointestinal side effects, renal calculi, and myocardial infarction 7.
• The risk-benefit effect of calcium supplementation is still a topic of debate, and more research is needed to determine the optimal dosage and form of calcium supplements for different populations 7.