The following additional adverse reactions have been reported during post-approval use and post-approval clinical trials with the active ingredient in paricalcitol capsules:
Immune System Disorders: Angioedema (including laryngeal edema)
Metabolism and Nutrition Disorders: Hypercalcemia
Investigations: Blood creatinine increased
Since paricalcitol is partially metabolized by CYP3A, exposure of paricalcitol will be increased while paricalcitol is co-administered with strong CYP3A inhibitors including the following drugs but not limited to: ketoconazole, atazanavir, clarithromycin, indinavir, itraconazole, nefazodone, nelfinavir, ritonavir, saquinavir, telithromycin or voriconazole. Dose adjustment of paricalcitol capsules may be required, and iPTH and serum calcium concentrations should be closely monitored if a patient initiates or discontinues therapy with a strong CYP3A4 inhibitor [see Clinical Pharmacology (12.3)].
Drugs that impair intestinal absorption of fat-soluble vitamins, such as cholestyramine, may interfere with the absorption of paricalcitol capsules.
The use of mineral oil or other substances that may affect absorption of fat may influence the absorption of paricalcitol capsules.
Pregnancy Category C.
Paricalcitol has been shown to cause minimal decreases in fetal viability (5%) when administered daily to rabbits at a dose 0.5 times a human dose of 14 mcg or 0.24 mcg/kg (based on body surface area, mcg/m2), and when administered to rats at a dose two times the 0.24 mcg/kg human dose (based on body surface area, mcg/m2). At the highest dose tested, 20 mcg/kg administered three times per week in rats (13 times the 14 mcg human dose based on surface area, mcg/m2), there was a significant increase in the mortality of newborn rats at doses that were maternally toxic and are known to produce hypercalcemia in rats. No other effects on offspring development were observed.
Paricalcitol was not teratogenic at the doses tested.
Paricalcitol (20 mcg/kg) has been shown to cross the placental barrier in rats. There are no adequate and well-controlled clinical studies in pregnant women. Paricalcitol capsules should be used during pregnancy only if the potential benefit to the mother justifies the potential risk to the fetus.
Studies in rats have shown that paricalcitol is present in the milk. It is not known whether paricalcitol is excreted in human milk. In the nursing patient, 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.
Safety and efficacy of paricalcitol capsules in pediatric patients have not been established.
Of the total number (n = 220) of CKD Stages 3 and 4 patients in clinical studies of paricalcitol capsules, 49% were age 65 and over, while 17% were age 75 and over. Of the total number (n = 88) of CKD Stage 5 patients in the pivotal study of paricalcitol capsules, 28% were age 65 and over, while 6% were age 75 and over. No overall differences in safety and effectiveness were observed between these patients and younger patients, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.
Excessive administration of paricalcitol capsules can cause hypercalcemia, hypercalciuria, and hyperphosphatemia, and over suppression of PTH [see Warnings and Precautions (5.1)].
Treatment of Overdosage
The treatment of acute overdosage of paricalcitol capsules should consist of general supportive measures. If drug ingestion is discovered within a relatively short time, induction of emesis or gastric lavage may be of benefit in preventing further absorption. If the drug has passed through the stomach, the administration of mineral oil may promote its fecal elimination. Serial serum electrolyte determinations (especially calcium), rate of urinary calcium excretion, and assessment of electrocardiographic abnormalities due to hypercalcemia should be obtained. Such monitoring is critical in patients receiving digitalis. Discontinuation of supplemental calcium and institution of a low-calcium diet are also indicated in accidental overdosage. Due to the relatively short duration of the pharmacological action of paricalcitol, further measures are probably unnecessary. If persistent and markedly elevated serum calcium levels occur, there are a variety of therapeutic alternatives that may be considered depending on the patient’s underlying condition. These include the use of drugs such as phosphates and corticosteroids, as well as measures to induce an appropriate forced diuresis.
Paricalcitol is not significantly removed by dialysis.
Paricalcitol, USP, the active ingredient in paricalcitol capsules, is a synthetically manufactured, metabolically active vitamin D analog of calcitriol with modifications to the side chain (D2) and the A (19-nor) ring. Paricalcitol is indicated for the prevention and treatment of secondary hyperparathyroidism in chronic kidney disease. Paricalcitol is available as soft gelatin capsules for oral administration containing 1 microgram, 2 micrograms or 4 micrograms of paricalcitol. Each capsule also contains medium chain triglycerides, alcohol, and butylated hydroxytoluene. The medium chain triglycerides are fractionated from coconut oil or palm kernel oil. The capsule shell is composed of gelatin, glycerin, titanium dioxide, iron oxide red (2 microgram capsules only), iron oxide yellow (2 microgram and 4 microgram capsules), iron oxide black (1 microgram capsules only), and water. The capsules are printed with black ink composed of purified water, black iron oxide, isopropyl alcohol, propylene glycol and hypromellose.
Paricalcitol is a white, crystalline powder with the empirical formula of C27 H44 O3 , which corresponds to a molecular weight of 416.64. Paricalcitol is chemically designated as 19-nor-1α,3β,25-trihydroxy-9,10-secoergosta-5(Z),7(E),22(E)-triene and has the following structural formula:
Secondary hyperparathyroidism is characterized by an elevation in parathyroid hormone (PTH) associated with inadequate levels of active vitamin D hormone. The source of vitamin D in the body is from synthesis in the skin as vitamin D3 and from dietary intake as either vitamin D2 or D3 . Both vitamin D2 and D3 require two sequential hydroxylations in the liver and the kidney to bind to and to activate the vitamin D receptor (VDR). The endogenous VDR activator, calcitriol [1,25(OH)2 D3 ], is a hormone that binds to VDRs that are present in the parathyroid gland, intestine, kidney, and bone to maintain parathyroid function and calcium and phosphorus homeostasis, and to VDRs found in many other tissues, including prostate, endothelium and immune cells. VDR activation is essential for the proper formation and maintenance of normal bone. In the diseased kidney, the activation of vitamin D is diminished, resulting in a rise of PTH, subsequently leading to secondary hyperparathyroidism and disturbances in the calcium and phosphorus homeostasis. Decreased levels of 1,25(OH)2 D3 have been observed in early stages of chronic kidney disease. The decreased levels of 1,25(OH)2 D3 and resultant elevated PTH levels, both of which often precede abnormalities in serum calcium and phosphorus, affect bone turnover rate and may result in renal osteodystrophy.
Paricalcitol is a synthetic, biologically active vitamin D2 analog of calcitriol. Preclinical and in vitro studies have demonstrated that paricalcitol’s biological actions are mediated through binding of the VDR, which results in the selective activation of vitamin D responsive pathways. Vitamin D and paricalcitol have been shown to reduce parathyroid hormone levels by inhibiting PTH synthesis and secretion.
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