CALCITRIOL INJECTION, USP

Excessive dosage of calcitriol injection induces hypercalcemia and in some instances hypercalciuria; therefore, early in treatment during dosage adjustment, serum calcium and phosphorus should be determined at least twice weekly. Should hypercalcemia develop, the drug should be discontinued immediately.

Calcitriol injection should be given cautiously to patients on digitalis, because hypercalcemia in such patients may precipitate cardiac arrhythmias.

The patient and his or her parents should be informed about adherence to instructions about diet and calcium supplementation and avoidance of the use of unapproved non-prescription drugs, including magnesium-containing antacids. Patients should also be carefully informed about the symptoms of hypercalcemia (see ADVERSE REACTIONS).

Serum calcium, phosphorus, magnesium and alkaline phosphatase and 24-hour urinary calcium and phosphorus should be determined periodically. During the initial phase of the medication, serum calcium and phosphorus should be determined more frequently (twice weekly).

Adynamic bone disease may develop if PTH levels are suppressed to abnormal levels. If biopsy is not being done for other (diagnostic) reasons, PTH levels may be used to indicate the rate of bone turnover. If PTH levels fall below recommended target range (1.5 to 3 times the upper limit of normal), in patients treated with calcitriol injection, the calcitriol injection dose should be reduced or therapy discontinued. Discontinuation of calcitriol therapy may result in rebound effect, therefore, appropriate titration downward to a maintenance dose is recommended.

Concomitant use of magnesium-containing preparations should be used with caution or avoided since such use may lead to the development of hypermagnesemia.

Corticosteroids with glucocorticoid activity may counteract the bone and mineral metabolism effects of vitamin D analogues.

Cytochrome P450 enzyme-inducing anticonvulsants such as carbamazepine, phenobarbital and phenytoin may reduce the effects of vitamin D because they increase vitamin D catabolism.

Long-term studies in animals have not been conducted to evaluate the carcinogenic potential of calcitriol injection. Calcitriol was not mutagenic in vitro in the Ames Test nor was oral calcitriol genotoxic in vivo in the Mouse Micronucleus Test. No significant effects on fertility and/or general reproductive performances were observed in a Segment I study in rats using oral calcitriol at doses of up to 0.3 mcg/kg.

Pregnancy: Teratogenic Effects: Pregnancy Category C

Calcitriol has been found to be teratogenic in rabbits when given orally at doses of 0.08 and 0.3 mcg/kg. All 15 fetuses in 3 litters at these doses showed external and skeletal abnormalities. However, none of the other 23 litters (156 fetuses) showed external and skeletal abnormalities compared with controls. Teratogenicity studies in rats at doses up to 0.45 mcg/kg orally showed no evidence of teratogenic potential. There are no adequate and well-controlled studies in pregnant women. Calcitriol injection should be used during pregnancy only if the potential benefits justifies the potential risk to the fetus.

It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from calcitriol, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

The safety and effectiveness of calcitriol injection were examined in a 12-week randomized, double-blind, placebo-controlled study of 35 pediatric patients, aged 13 to 18 years, with end-stage renal disease on hemodialysis. Sixty-six percent of the patients were male, 57% were African-American, and nearly all had received some form of vitamin D therapy prior to the study. The initial dose of calcitriol was 0.5 mcg, 1.0 mcg, or 1.5 mcg, 3 times per week, based on baseline iPTH level of less than 500 pg/mL, 500-1000 pg/mL, or greater than 1000 pg/mL, respectively. The dose of calcitriol was adjusted in 0.25 mcg increments based on the levels of serum iPTH, calcium, and Ca x P. The mean baseline levels of iPTH were 769 pg/mL for the 16 calcitriol-treated patients and 897 pg/mL for the 19 placebo-treated subjects. The mean weekly dose of calctiriol ranged from 1.0 mcg to 1.4 mcg. In the primary efficacy analysis, 7 of 16 (44%) subjects in the calcitriol group had 2 consecutive 30% decreases from baseline iPTH compared with 3 to 19 (16%) patients in the placebo group (95% CI for the difference between groups -6%, 62%). One calcitriol-treated patient experienced transient hypercalcemia (>11.0 mg/dL), while 6 of 16 (38%) calcitriol-treated patients vs. 2 of 19 (11%) placebo-treated patients experienced Ca x P>75.

Clinical studies of calcitriol injection did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosage range, reflecting greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

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

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, nephrocalcinosis, sensory disturbance, dehydration, apathy, and, rarely, overt psychosis.

Occasional mild pain on injection has been observed.

Rare cases of hypersensitivity reactions have been reported, including anaphylaxis.

General treatment of hypercalcemia (greater than 1 mg/dL above the upper limit of normal range) consists of immediate discontinuation of calcitriol injection therapy, institution of a low calcium diet and withdrawal of calcium supplements. Serum calcium levels should be determined daily until normocalcemia ensues. Hypercalcemia usually resolves in two to seven days. When serum calcium levels have returned to within normal limits, Calcitriol Injection therapy may be reinstituted at a dose 0.5 mcg less than prior therapy. Serum calcium levels should be obtained at least twice weekly after all dosage changes.

Persistent or markedly elevated serum calcium levels may be corrected by dialysis against a calcium-free dialysate.

The treatment of acute accidental overdosage of calcitriol injection should consist of general supportive measures. Serial serum electrolyte determinations (especially calcium), rate of urinary calcium excretion and assessment of electrocardiographic abnormalities due to the hypercalcemia should be obtained. Such monitoring is critical in patients receiving digitalis. Discontinuation of supplemental calcium and low calcium diet are also indicated in accidental overdosage. Due to the relatively short duration of the pharmacological action of calcitriol, further measures are probably unnecessary. Should, however, persistent and markedly elevated serum calcium levels occur, there are a variety of therapeutic alternatives which may be considered, depending on the patients' underlying condition. These include the use of drugs such as phosphates and corticosteroids as well as measures to induce an appropriate forced diuresis. The use of peritoneal dialysis against a calcium-free dialysate has also been reported.

Storage: Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].

Protect from light.

AKORN
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Gurnee, IL 60031

CL00N
Rev. 05/22