Paricalcitol therapy for secondary hyperparathyroidism in patients on maintenance hemodialysis previously treated with calcitriol: A single-center crossover study

Three Therapeutic Strategies: Cinacalcet, Paricalcitol or Both in Secondary Hyperparathyroidism Treatment in Hemodialysed Patients During 1-Year Observational Study-A Comparison

Introduction: Secondary hyperparathyroidism (sHPT) is a common hormonal complication of chronic kidney disease. There are several therapeutic options for sHPT management aiming at calcium-phosphorus balance normalization and decrease of parathormone secretion. Objectives: The aim of this retrospective, observational study was the outcome assessement of three most common therapeutic strategies of secondary hyperparathyroidism treatment with vitamin D receptor activator-paricalcitol, calcimimetic-cinacalcet or both agents administered together during in 12-months period. Methods: One hundred and thirty-one haemodialysed patients with uncontrolled parathyroid hormone secretion have been treated with paricalcitol administered intravenously (group PAR-60 patients) or cinacalcet per os (group CIN-50 patients). The last group (group PAR+CIN-21 patients) received paricalcitol i.v. and oral cinacalcet administered simultaneously. Results: In all groups, the iPTH level decreased significantly, however in group 1 treated with paricalcitol administered intravenously iPTH level decrease was greater than in group 2 treated with cinacalcet and in group 3 treated with paricalcitol and cinacalcet in parallel. The most substantial change of iPTH level was noticed after 3-months of observation. After this period the iPTH level was stabilized and maintained till the end of observation. Safety level of all strategies was comparable. No severe hypercalcemia or hypocalcemia was observed during the whole period of observation. Conclusions: The results of observation show significant advantage of intravenous paricalcitol treatment. Complementing cinacalcet therapy with paricalcitol does not improve treatment outcomes. In case of unsatisfactory results after 3-months treatment, potential continuation should be considered carefully. Among three available therapeutic options, the treatment with paricalcitol i.v. should be considered in all haemodialysed patients with inadequate control of serum PTH level. The second option-with cinacalced administered orally should be considered in PD patients and when severe hypercalcemia occurs.

Differential influence of vitamin D analogs on left ventricular mass index in maintenance hemodialysis patients

PURPOSE

Secondary hyperparathyroidism (SHPT) is a common feature in maintenance hemodialysis (MHD) patients. Inadequate treatment of SHPT has been associated with cardiovascular complications, and vitamin D therapy might influence the development of cardiovascular diseases. In the present study, we aimed to evaluate the effects of intravenous paricalcitol and calcitriol treatments on left ventricular mass index changes in MHD patients.

METHODS

We conducted an observational study with a 12-month follow-up duration to compare the outcomes of intravenous paricalcitol and calcitriol treatments in MHD patients. Eighty patients with moderate to severe SHPT were enrolled in the study. All the patients had normalized total serum Ca concentration <10.5 mg/dL, serum calcium-phosphorus product (Ca × P) <75, and parathyroid hormone level (PTH) level ≥300 pg/mL at the begining of the follow-up period.

RESULTS

The patients were divided into a paricalcitol group (n = 40) and a calcitriol group (n = 40). The demographic, clinical, and biochemical characteristics of the patients were similar at baseline. We observed significantly superior control of SHPT; lesser frequency of hypercalcemia and hyperphosphatemia, and Ca × P level elevations; and interruption of vitamin D treatment in the paricalcitol group. Moreover, we found no significant change in left ventricular mass index in the paricalcitol group, but found a significantly increased left ventricular mass index in the calcitriol group during the follow-up period (from 136.6 ± 35.2 g/m2 to 132.9 ± 40.4 g/m2 vs. from 137.2 ± 30.1 g/m2 to 149.4 ± 31.0 g/m2; p<0.044).

CONCLUSION

We observed that, compared with calcitriol therapy, paricalcitol therapy reduced the PTH concentrations more effectively without causing hypercalcemia and hyperphosphatemia and might have a substantial beneficial effect on the development of left ventricular hypertrophy.

Vitamin D receptor activator selectivity in the treatment of secondary hyperparathyroidism: understanding the differences among therapies

Secondary hyperparathyroidism (SHPT) is a common and serious consequence of chronic kidney disease (CKD). SHPT is a complex condition characterised by a decline in 1,25-dihydroxyvitamin D and consequent vitamin D receptor (VDR) activation, abnormalities in serum calcium and phosphorus levels, parathyroid gland hyperplasia, elevated parathyroid hormone (PTH) secretion, and systemic mineral and bone abnormalities. There are three classes of drugs used for treatment of SHPT: (i) nonselective VDR activators or agonists (VDRAs); (ii) selective VDRAs; and (iii) calcimimetics. The VDRAs act on the VDR, whereas the calcimimetics act on the calcium-sensing receptor. Calcimimetics are commonly used in conjunction with VDRA therapy. By virtue of the differences in their chemical structure, the nonselective and selective VDRAs differ in their effects on gene expression, and ultimately parathyroid gland, bone and intestine function. Medications in all three classes are effective in suppression of PTH; however, clinical studies show that calcimimetics are associated with an unfavourable tolerability profile and hypocalcaemia, whereas nonselective VDRAs, and to a lesser extent selective VDRAs, are associated with dose-limiting hypercalcaemia and hyperphosphataemia. Selective VDRAs also have minimal undesirable effects on calcium absorption in the intestine, and calcium and phosphorus mobilisation in the bone compared with nonselective VDRAs. Calcium load in patients with CKD can lead to vascular calcification, accelerated progression of cardiovascular disease and increased mortality. High serum phosphorus levels are also associated with adverse effects on cardiorenal function and survival. Recent evidence suggests that VDRAs are associated with a survival benefit in CKD patients, with a more favourable effect with selective VDRAs than nonselective VDRAs. Paricalcitol, a selective VDRA, is reported to exert specific effects on gene expression in various cell types that are involved in vascular calcification and the development of coronary artery disease. This article examines the molecular mechanisms that determine selectivity of VDRAs, and reviews the evidence for clinical efficacy, safety and survival associated with the three drug classes used for treatment of SHPT in CKD patients.