Effectiveness of Calcium Supplements for Treating Hypocalcemia

As seen in the Consultant Connection March 2014 Issue
Jeremy Webster, PharmD Candidate, Ohio Northern University

Many people do not consume anywhere near the recommended amount of calcium in their diets and regularly take calcium (& vitamin D) supplements to maintain normal calcium levels in the body (total calcium: 8.4-10.2 mg/dl; ionized: 3.8-5.3 mg/dl) and to prevent the problems caused by hypocalcemia (i.e. osteoporosis and broken bones).  However, recent studies have indicated questionable efficacy of calcium supplements in preventing bone fractures and they have also been found to potentially cause an increased risk of heart attacks and death.  This has not been thoroughly studied and requires future research to confirm these claims. However, it may be necessary to use calcium supplementation treatment to avoid the potentially serious symptoms of hypocalcemia. 
Symptoms of hypocalcemia are usually observed when calcium levels are ~7-7.5 mg/dl (or <2.8 mg/dl ionized calcium) and can very in severity from asymptomatic to seizures, QT prolongation, and life-threatening tetany, so it is important to address low calcium levels.  However, there are many causes of hypocalcemia and supplements may not necessarily be needed to correct the problem. Other imbalances that can cause hypocalcemia should be addressed before supplemental calcium is given. A few common causes are listed below. 
  1. Vitamin D deficiency: causes decreased calcium absorption
    • Treatment: 50,000 IU 25-hydroxyvitamin D or 0.25-0.5mg 1,25-hydroxyvitamin D
  2. Low magnesium: makes it difficult to normalize calcium and potassium levels and should be corrected in every patient
    • Treatment: 2g magnesium sulfate over 10 to 15 minutes, then 1 g/hr
  3. High phosphate: usually resolves with intact renal function
    • Treatment: saline + 10-15mg/kg acetazolamide every 3-4 hours
    • Hemodialysis may be needed (especially if impaired renal function)
  4. Alkalosis: increases calcium binding to albumin and decreases ionized calcium available; increases severity of symptoms
    • Treatment of metabolic acidosis can have the same effect
Acute symptomatic hypocalcemia (total calcium <7.0 mg/dl or ionized calcium <0.8 mmol) should be treated immediately due to the risk of severe symptoms. The most appropriate treatment (unless there is low magnesium levels) is IV calcium in the form of calcium gluconate. Calcium chloride is not preferred because it causes more tissue necrosis if extravasated. 
  • IV dosing: 100-200mg of elemental calcium (1-2g calcium gluconate diluted in saline or dextrose) initially over 10-20 min, then a slow infusion at 0.5-1.5 mg/kg/hr 
  • Continue slow infusion until the patient is receiving effective doses of oral calcium + vitamin D
Chronic hypocalcemia should be treated with oral calcium supplement therapy with a target calcium level of 8.0 because most patients will be asymptomatic and higher levels can cause hypercalciuria. Oral vitamin D supplementation may be needed as well if calcium supplements alone do not achieve the desired calcium level. 
  • Oral dosing: ~1-2 g/day (elemental calcium) in 2-4 divided doses with food
    • Ex. 500-1000mg CaCO3 (200-400mg elemental calcium) four times a day 
When adequate blood levels of calcium are reached with supplementation, it is important to measure urinary calcium excretion and a thiazide diuretic may be added if hypercalciuria is detected to prevent complications including kidney stones and renal impairment.  Serum calcium levels should also be monitored closely at first and then every 3-6 months when controlled.
In conclusion, the best way to maintain normal calcium levels in the body and prevent all of the potential complications caused by hypocalcemia (or treatment of hypocalcemia) is to consume the recommended amount of dietary calcium every day from foods/drinks such as milk, yogurt, almonds, kale, broccoli, and calcium-fortified orange juice, etc. However, symptomatic hypocalcemia should not be left untreated due to the potential severity of the symptoms.  As far as chronic hypocalcemia, calcium supplementation should be used as recommended until further studies prove that it is not beneficial or that the potential risks of the treatment outweigh the potential benefits. 
Skugor, Mario. “Hypocalcemia.” Cleveland Clinic Medical Publications: Disease Management Project. January 2009. Available from: <http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/endocrinology/hypocalcemia/>.
Calcium Supplements/Hypocalcemia. GlobalRPh [database on internet]. 2013 [cited 2013 Nov 19]. Available from: <http://www.globalrph.com/calcium_supplements.htm>.
Houtkooper, Linda, Farrell, Vanessa. “Calcium Supplement Guidelines.” The University of Arizona: Arizona Cooperative Extension. Revised January 2011. Available from: <http://ag.arizona.edu/pubs/health/az1042.pdf>.
Brody, Jane. “Thinking Twice About Calcium Supplements.” The New York Times: Personal Health. 2013 April 8. Available from: <http://well.blogs.nytimes.com/2013/04/08/thinking-twice-about-calcium-supplements-2/?_r=0>.
LexiComp [database on the Internet]. Hudson (OH): LexiComp. 2013 [cited 2013 Nov 19]. Available from: http://online.lexi.com/crlsql/servlet/crlonline

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