Calcitriol Injection Rx Only

Calcitriol Injection is synthetically manufactured calcitriol and is available as a sterile, isotonic, clear, colorless to yellow, aqueous solution for intravenous injection. Calcitriol Injection is available in 1 mL ampules. Each 1 mL contains calcitriol 1 mcg; polysorbate 20, 4 mg; edetate disodium dehydrate 1.1 mg; sodium phosphate dibasic 7.6 mg; sodium phosphate monobasic 1.8 mg; sodium chloride 1.5 mg; sodium ascorbate 10 mg. pH 6.6 (5.9 - 7.0).

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-1-(alpha),3 (beta),25-triol and has the following structural formula:

Molecular Formula: C₂₇H₄₄O₃

The other names frequently used for calcitriol are 1(alpha),25-dihydroxycholecalciferol, 1(alpha),25-dihydroxyvitamin D₃, 1,25-DHCC, 1,25(OH)₂D₃ and 1,25-diOHC.

Calcitriol is the active form of Vitamin D₃ (cholecalciferol). The natural or endogenous supply of vitamin D in man mainly depends on ultraviolet light for conversion of 7-dehydrocholesterol to vitamin D₃ in the skin. Vitamin D₃ 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 D₃-25-hydroxylase enzyme present in the liver, and the product of this reaction is 25-(OH)D₃ (calcifediol). The latter undergoes hydroxylation in the mitochondria of kidney tissue, and this reaction is activated by the renal 25-hydroxyvitamin D₃-1-(alpha)-hydroxylase to produce 1,25-(OH)₂D₃ (calcitriol), the active form of vitamin D₃.

The known sites of action of calcitriol are intestine, bone, kidney and parathyroid gland. Calcitriol is the most active known form of vitamin D₃ 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)₃D₃ and to calcitroic acid.

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.

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 phosphorus levels in patients undergoing dialysis.

Overdosage of any form of vitamin D is dangerous (see also OVERDOSAGE). Progressive hypercalcemia due to overdosage of vitamin D and its metabolites may be so severe as to require emergency attention. Chronic hypercalcemia can lead to generalized vascular calcification, nephrocalcinosis and other soft-tissue calcification. The serum calcium times phosphate (Ca x P) product should not be allowed to exceed 70. Radiographic evaluation of suspect anatomical regions may be useful in the early detection of this condition.

Adverse effects of Calcitriol Injection are, in general, similar to those encountered with excessive vitamin D intake. The early and late signs and symptoms of vitamin D intoxication associated with hypercalcemia include:

1. Early

Weakness, headache, somnolence, nausea, vomiting, dry mouth, constipation, muscle pain, bone pain and metallic taste.

2. Late

Polyuria, polydipsia, anorexia, weight loss, nocturia, conjunctivitis (calcific), pancreatitis, photophobia, rhinorrhea, pruritus, hyperthermia, decreased libido, elevated BUN, albuminuria, hypercholesterolemia, elevated SGOT and SGPT, ectopic calcification, hypertension, cardiac arrhythmias and, rarely, overt psychosis. Occasional mild pain on injection has been observed.

Administration of Calcitriol Injection to patients in excess of their requirements can cause hypercalcemia, hypercalciuria and hyperphosphatemia. High intake of calcium and phosphate concomitant with Calcitriol Injection may lead to similar abnormalities.

The optimal dose of Calcitriol Injection must be carefully determined for each patient.

The effectiveness of Calcitriol Injection therapy is predicated on the assumption that each patient is receiving an adequate and appropriate daily intake of calcium. The RDA for calcium in adults is 800 mg. To ensure that each patient receives an adequate daily intake of calcium, the physician should either prescribe a calcium supplement or instruct the patient in proper dietary measures.

The recommended initial dose of Calcitriol Injection, depending on the severity of the hypocalcemia and/or secondary hyperparathyroidism, is 1 mcg (0.02 mcg/kg) to 2 mcg administered three times weekly, approximately every other day. Doses as small as 0.5 mcg and as large as 4 mcg three times weekly have been used as an initial dose. If a satisfactory response is not observed, the dose may be increased by 0.5 to 1 mcg at two to four week intervals. During this titration period, serum calcium and phosphorus levels should be obtained at least twice weekly. If hypercalcemia or a serum calcium times phosphate product greater than 70 is noted, the drug should be immediately discontinued until these parameters are appropriate. Then, the Calcitriol Injection dose should be reinitiated at a lower dose. Doses may need to be reduced as the PTH levels decrease in response to the therapy. Thus, incremental dosing must be individualized and commensurate with PTH, serum calcium and phosphorus levels. The following is a suggested approach in dose titration:

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

Discard unused portion.

Calcitriol Injection is supplied as follows:

Manufactured by:
Julphar, United Arab Emirates

Distributed by:
West-ward Pharmaceutical Corp.
Eatontown, NJ 07724  USA

Revised November 2009

NDC# 0143-9728-05

Calcitriol Injection
1 mcg/mL

1 mL Single Dose Vials
For IV Injection Only