Experience with Cinacalcet for Secondary Hyperparathyroidism in Patients with Chronic Kidney Disease Stage III and IV

Dysequilibrium in calcium and phosphate metabolism with development of secondary hyperparathyroidism (SHPT) is common in patients with chronic kidney disease (CKD) stage III and IV. Dietary phosphate restrictions and calcium based oral phosphate binders have not been effective in all subjects with SHPT, and soft tissue and vascular calcifications with an increased risk of cardiovascular death related are known consequences. Treatment with the calcimimetic Cinacalcet (Cc) has contributed to a better calcium and phosphate control in patients given hemodialysis treatment. In this retrospective study we present our experience with Cc given to ten (one year) or five (two years) patients with CKD stage III and IV and SHPT not suitable for surgery. With conventional therapy target levels of intact parathyroid hormon (iPTH) are seldomly reached the reason why an iPTH value < 300 ng/l was considered acceptable. Levels of iPTH decreased significantly after 3 months of Cc treatment and remained at the lower level. Plasma ionized-Ca (Ca) concentrations decreased initially but remained above 1.00 mmol/l in all but one patient. Phophate (P) levels increased to 1.41 ± 0.09 mmol/l (mean ± SE) leaving the Ca × P product unchanged. While patients with high iPTH needed high Cc doses up to 90 mg/day, some of the patients required very low doses 4.5-20 mg/day in order to achieve a decrease in iPTH levels. Only one patient reported gastric pain needing dose reduction and other adverse effects were not found. No changes in QT-time were observed. We experienced that Cc treatment was promising to control SHPT and stabilized the Ca-P balance in patients with CKD stage III and IV. Dosing may be challenging and laboratory values should be controlled often (monthly) as these patients may have variable response to Cc treatment. Due to the minimal knowledge about its effect on morbidity and mortality in the predialytic population further controlled studies are needed to confirm its efficacy and safety.