PHILADELPHIA—Serum phosphorus levels in hemodialysis (HD) patients with secondary hyperparathyroidism (SHPT) decrease during treatment with cinacalcet, data presented at Kidney Week 2011 show. This effect occurs regardless of baseline SHPT severity.

Kerry Cooper, MD, and colleagues at Amgen, Inc., which makes cinacalcet, evaluated the relationship between parathyroid hormone (PTH) and serum phosphorus before and during 26 weeks of treatment with cinacalcet using pool data from phase 3 studies. The study population included 656 patients. All patients had a PTH level greater than 300 pg/mL and calcium level of 8.4 mg/L or higher at study entry. SHPT severity was categorized by PTH levels: 300-500, 500-800, and greater than 800 pg/mL.

The median serum phosphorus at baseline was incrementally higher by category of SHPT severity, being highest in those with PTH levels greater than 800 pg/mL.

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Median baseline serum phosphorus levels in the 300-500, 500-800, and greater than 800 pg/mL groups were 5.82, 5.88, and 6.55 mg/dL, respectively. The mean phosphorus levels during treatment with cinacalcet were 5.21, 5.28, and 5.64 mg/dL, respectively, which translated into phosphorus reductions of 7.95%, 10.11%, and 12.46%.

The authors concluded that inadequately controlled SHPT contributes substantially to the hyperphosphatemia among HD patients.