CALCIJEX®(calcitriol injection)1 mcg/mL
Calcijex (calcitriol injection) is synthetically manufactured calcitriol and is available as a sterile, isotonic, clear, colorless to yellow, aqueous solution for intravenous injection. Calcijex is available in 1 mL ampuls. Each 1 mL contains calcitriol, 1 mcg; Polysorbate 20, 4 mg; sodium ascorbate 2.5 mg added. May contain hydrochloric acid and/or sodium hydroxide for pH adjustment. pH is 6.5 (5.9 to 7.0). Contains no more than 1 mcg/mL of aluminum.

Calcitriol is a crystalline compound which occurs naturally in humans. It is soluble in organic solvents but relatively insoluble in water.

Calcitriol is chemically designated (5Z,7E)-9, 10-secocholesta-5,7,10(19)-triene-1α,3β,25-triol and has the following structural formula:
Molecular Formula: CHO

The other names frequently used for calcitriol are 1α,25-dihydroxycholecalciferol, 1α,25-dihydroxyvitamin D, 1,25-DHCC, 1,25(OH)D and 1,25-diOHC.

Calcitriol is the active form of vitamin D (cholecalciferol). The natural or endogenous supply of vitamin D in man mainly depends on ultraviolet light for conversion of 7-dehydrocholesterol to vitamin D in the skin. Vitamin D must be metabolically activated in the liver and the kidney before it is fully active on its target tissues. The initial transformation is catalyzed by a vitamin D-25-hydroxylase enzyme present in the liver, and the product of this reaction is 25-(OH)D (calcifediol). The latter undergoes hydroxylation in the mitochondria of kidney tissue, and this reaction is activated by the renal 25-hydroxyvitamin D-1-α-hydroxylase to produce 1,25-(OH)D (calcitriol), the active form of vitamin D.

The known sites of action of calcitriol are intestine, bone, kidney and parathyroid gland. Calcitriol is the most active known form of vitamin D in stimulating intestinal calcium transport. In acutely uremic rats, calcitriol has been shown to stimulate intestinal calcium absorption. In bone, calcitriol, in conjunction with parathyroid hormone, stimulates resorption of calcium; and in the kidney, calcitriol increases the tubular reabsorption of calcium. In vitro and in vivo studies have shown that calcitriol directly suppresses secretion and synthesis of PTH. A vitamin D-resistant state may exist in uremic patients because of the failure of the kidney to adequately convert precursors to the active compound, calcitriol.

Calcitriol when administered by bolus injection is rapidly available in the blood stream. Vitamin D metabolites are known to be transported in blood, bound to specific plasma proteins. The pharmacologic activity of an administered dose of calcitriol is about 3 to 5 days. Two metabolic pathways for calcitriol have been identified, conversion to 1,24,25-(OH)D and to calcitroic acid.

Calcijex (calcitriol injection) is indicated in the management of hypocalcemia in patients undergoing chronic renal dialysis. It has been shown to significantly reduce elevated parathyroid hormone levels. Reduction of PTH has been shown to result in an improvement in renal osteodystrophy.

Calcijex (calcitriol injection) should not be given to patients with hypercalcemia or evidence of vitamin D toxicity.

Since calcitriol is the most potent metabolite of vitamin D available, vitamin D and its derivatives should be withheld during treatment.

A non-aluminum phosphate-binding compound should be used to control serum phosph