Paricalcitol in Dialysis Patients with Calcitriol - Resistant Secondary Hyperparathyroidism

Background. Clinical studies in dialysis patients with secondary hyperparathyroidism (SHPT) showed that paricalcitol (19-nor-1a, 25-dihydroxyvitamin D2), a vitamin D analog, suppresses parathyroid hormone (PTH) levels as effectively as intravenous calcitriol without resulting in significant increases in serum Ca and P. The aim of the present study is to investigate whether paricalcitol could provide long-term control of moderate to severe SHPT in hemodialysis patients considered resistant to intravenous calcitriol/alfacalcidol therapy. We also assess the incidence of hypercalcemia and hyperphosphatemia during treatment with paricalcitol in this group of patients. Methods. Thirty-one stable hemodialysis patients of mean age 54±10 with persistent intact PTH (iPTH) levels of 600 pg/ml or greater for at least 6 months despite treatment with intravenous alfacalcidol were included into the study. All patients underwent hemodialysis three times weekly. Paricalcitol was administered intravenously 3 times per week at the end of hemodialysis session. Therapy with paricalcitol was not initiated until a patient’s serum P level was less than 6,5 mg/dl (2,1 mmol/L). Nutritional counseling and phosphate binders (calcium acetate and/or sevelamer) were used for phosphate control. The initial dose of paricalcitol in mcg per hemodialysis session was calculated according to the formula: iPTH/100. Subsequent doses were titrated according to serum levels of iPTH, Ca and P. The follow-up of the patients was 12-18 months. During the study serum levels of Ca and P were measured every month and iPTH every 1-3 months. The serum Ca concentration was corrected according to the formula: total Ca + 0,8 × (4 – serum albumin). Results. Mean iPTH levels (baseline mean 933±294 pg/ml) decreased rapidly during the first months of therapy and this decrease reached statistical significance already by the first month of treatment with paricalcitol. Mean iPTH levels reached the designated target range (100-300 pg/ml) by month 5 (mean 242±199 pg/ml). Mean Ca and P levels did not change significantly over the 14 months of paricalcitol