Principles of Treatment of Hypocalcemia - The Merck Veterinary Manual

Principles of Treatment of Hypocalcemia

The definitive treatment for hypocalcemia is to eliminate the underlying cause. Supportive measures, including the following, to restore normocalcemia can be administered pending the diagnosis.

Parenteral Calcium:

Hypocalcemic tetany or convulsions are indications for the immediate IV administration of 10% calcium gluconate (1.0-1.5 mL/kg), which should be slowly infused over a 10-min period. Close monitoring is mandatory; if bradycardia or shortening of the QT interval occurs, the IV infusion should be slowed or temporarily discontinued.

Once the life-threatening signs of hypocalcemia have been controlled, calcium can be added to the IV fluids and administered as a slow continuous infusion (eg, 10% calcium gluconate, 2.5 mL/kg every 6-8 hr). The rate of calcium administration should be adjusted as necessary to maintain a normal serum calcium concentration, and the infusion should be continued for as long as necessary to prevent recurrence of hypocalcemia. Although this continuous calcium infusion will maintain normocalcemia, its effects are short-lived; hypocalcemia will recur within hours of stopping the infusion unless other treatment is given.

Oral Calcium:

Oral calcium supplementation may be beneficial in some conditions (eg, hypoparathyroidism, puerperal tetany). The daily requirements are 1-4 g for dogs and 0.5-1 g for cats. The daily dose of calcium should be based on the amount of elemental calcium in the product, rather than on the weight of the calcium salt.

Vitamin D:

In some conditions, vitamin D supplementation is necessary to increase calcium absorption from the intestines. There are 3 main preparations of vitamin D available, including vitamin D₂ (ergocalciferol), dihydrotachysterol, and 1,25-dihydroxyvitamin D (calcitriol). The dosage and duration of response of these drugs depends on the form used. For vitamin D₂, the initial required dosages are generally 4,000-6,000 IU/kg/day, whereas the final dosages required to maintain normocalcemia range from 1,000-2,000 IU/kg, once daily to once weekly. For dihydrotachysterol, initial loading dosages of 0.02-0.03 mg/kg/day are usually administered, with maintenance dosages of 0.01-0.02 mg/kg given every 24-48 hr. For 1,25-dihydroxyvitamin D, a daily dosage of 0.025-0.06 µg/kg (25-60 ng/kg/day) is generally required. Because the available capsule sizes (250 and 500 ng) are not well formulated for the small body size of most dogs and cats, and these capsules cannot be readily divided, it may be desirable to contact a pharmacist who can reformulate these products to a size that is appropriate for the individual pet. With all vitamin D preparations and dosage regimens, the development of iatrogenic hypercalcemia is a common complication of treatment.