CLINICAL STUDIES

14 Effectiveness of calcium acetate in decreasing serum phosphorus has been demonstrated in two studies of the calcium acetate solid oral dosage form. Ninety-one patients with end-stage renal disease who were undergoing hemodialysis and were hyperphosphatemic (serum phosphorus >5.5 mg/dL) following a 1-week phosphate binder washout period contributed efficacy data to an open-label, non-randomized study. The patients received calcium acetate 667 mg tablets at each meal for a period of 12 weeks. The initial starting dose was 2 tablets per meal for 3 meals a day, and the dose was adjusted as necessary to control serum phosphorus levels. The average final dose after 12 weeks of treatment was 3.4 tablets per meal. Although there was a decrease in serum phosphorus, in the absence of a control group the true magnitude of effect is uncertain. The data presented in Table 2 demonstrate the efficacy of calcium acetate in the treatment of hyperphosphatemia in end-stage renal disease patients. The effects on serum calcium levels are also presented. Table 2: Average Serum Phosphorous and Calcium Levels at Pre-Study, Interim, and Study Completion Time Points Parameter Pre-Study Week 4 b Week 8 Week 12 p-valuec Phosphorus (mg/dL) a 7.4 ± 0.17 5.9 ± 0.16 5.6 ± 0.17 5.2 ± 0.17 ≤0.01 Calcium (mg/dL) a 8.9 ± 0.09 9.5 ± 0.10 9.7 ± 0.10 9.7 ± 0.10 ≤0.01 a Values expressed as mean ± SE. b Ninety-one patients completed at least 6 weeks of the study. c ANOVA of difference in values at pre-study and study completion. There was a 30% decrease in serum phosphorus levels during the 12 week study period (p<0.01). Two-thirds of the decline occurred in the first month of the study. Serum calcium increased 9% during the study mostly in the first month of the study. Treatment with the phosphate binder was discontinued for patients from the open-label study, and those patients whose serum phosphorus exceeded 5.5 mg/dL were eligible for entry into a double-blind, placebo-controlled, cross-over study. Patients were randomized to receive calcium acetate or placebo, and each continued to receive the same number of tablets as had been individually established during the previous study. Following 2 weeks of treatment, patients switched to the alternative therapy for an additional 2 weeks. The phosphate binding effect of calcium acetate is shown in the Table 3. Table 3: Serum Phosphorous and Calcium Levels at Study Initiation and After Completion of Each Treatment Arm Parameter Pre-Study Post-Treatment p-valueb Calcium Acetate Placebo Phosphorus (mg/dL)a 7.3 ± 0.18 5.9 ± 0.24 7.8 ± 0.22 <0.01 Calcium (mg/dL)a 8.9 ± 0.11 9.5 ± 0.13 8.8 ± 0.12 <0.01 a Values expressed as mean ± SEM. b ANOVA of calcium acetate vs. placebo after 2 weeks of treatment. Overall, 2 weeks of treatment with calcium acetate statistically significantally (p<0.01) decreased serum phosphorus by a mean of 19% and increased serum calcium by a statistically significant (p<0.01) but clinically unimportant mean of 7%.