Clinical Uses of 1,25-dihydroxy-19-nor-vitamin D2 (Paricalcitol)

The activation of vitamin D receptors (VDR) - (including activation by 25-hydroxyvitamin D) -seems to have not only mineral-metabolism beneficial effects but also important extra-skeletal actions. Paricalcitol is a synthetic vitamin D-2 agonist of the VDR approved for the prevention and treatment of secondary hyperparathyroidism associated with chronic kidney disease (CKD). As a result of its selectivity, paricalcitol provides a wider therapeutic window for PTH suppression, minimizing deleterious effects of high serum calcium and/or phosphate concentrations. Paricalcitol also shares, and sometimes improves pleiotropic vitamin-D related systemic effects. For instance, paricalcitol has been repeatedly shown to decrease calcium and phosphate deposition in vessels and to decrease the expression of osteogenic factors preventing the active transformation of smooth muscle vascular cells into osteoblast-like cells in experimental models. In patients, paricalcitol has been associated with improved survival of dialysis patients and it may improve residual albuminuria in diabetic patients. Consequently, paricalcitol may enhance the standard of care in these high-risk patients. Although it seems reasonable to use these potential advantages to guide the individual and integral management of the complex CKD-mineral and bone disorder, it is necessary to recognize that many of these observations have not been proven nor confirmed in prospective clinical trials.