Long-term effect of oral calcitriol pulse therapy on bone in hemodialysis patients

Effect of 22-oxacalcitriol on bone histology of hemodialyzed patients with severe secondary hyperparathyroidism

To examine the effectiveness of 22-oxacalcitriol (OCT) injection on the improvement of severe osteitis fibrosa, we studied 10 hemodialyzed patients (age, 59 +/- 12 years). The initial OCT dose was 5 microg and was administered three times weekly at the end of each hemodialysis session. OCT doses (1, 3, 5, 10, 15, and 20 microg) were changed in subsequent weeks to maintain serum calcium levels at less than 11.5 mg/dL. Administration of OCT significantly suppressed serum intact parathyroid hormone (PTH) from an initial level of 1,193 +/- 584 to 775 +/- 552 pg/mL in the 24th week (n = 10). OCT increased PTH levels again to 857 +/- 635 pg/mL in the 48th week (n = 7). Among the 10 patients, 5 patients (high responders) showed more than a 50% suppression of serum intact PTH levels at the end of the study. The rest of the patients had hypercalcemia and did not receive increased OCT doses (low responders). At the start of the treatment, the only difference between high and low responders was serum calcium level. Serum calcium levels (adjusted for serum albumin level) increased from 9.7 +/- 0.7 mg/dL (n = 10) at the beginning to 10.5 +/- 0.6 mg/dL (n = 10) in the 24th week and to 11. 1 +/- 0.7 mg/dL (n = 7) in the 48th week. Six patients (1 to 6) agreed to undergo a second bone biopsy in the 24th week of OCT administration. In bone histomorphometric measurements, OCT significantly changed bone marrow fibrosis, mineralization (labeled mineralizing surface and bone formation rate), and osteoid formation (osteoid volume and thickness). In conclusion, intravenous OCT effectively suppressed PTH secretion and improved the bone histological characteristics of severe osteitis fibrosa, especially in patients with initial serum calcium levels less than 10 mg/dL. With concerns about OCT causing adynamic bone, additional bone histological data are needed to ensure the long-term safety of OCT.

Effect of administering calcium carbonate to treat secondary hyperparathyroidism in nondialyzed patients with chronic renal failure

We administered calcium carbonate orally to determine its safety and efficacy in treating nondialyzed patients with mild to moderate renal failure and secondary hyperparathyroidism. Twenty patients with chronic renal failure (creatinine clearance levels ranging from 7.9 to 42.7 mL/min) participated in this study. After a 6-month control period, 3 g calcium carbonate was administered daily for 6 months. We studied the effect for another 6 months after discontinuation of the regimen. We found that serum-intact parathyroid hormone was suppressed from 183 +/- 149 pg/mL to 85 +/- 61 pg/mL (P < 0.05) by treatment. This suppression was achieved with no increase in serum concentrations of 1,25(OH)2D3. Serum phosphorus levels decreased from 3.4 +/- 0.7 to 3.0 +/- 0.7 mg/dL (P < 0.01) and Ca2+ concentration increased significantly from 2.40 +/- 0.12 mEq/L to 2.57 +/- 0.08 mEq/L (P < 0.001) at 6 months. These changes were reversed after the 6-month period of withdrawal from calcium carbonate. Deterioration of renal function was not exacerbated by the therapy. Calcium carbonate administration also suppressed the serum concentrations of alkaline phosphatase and osteocalcin, indicating that improvement of hyperparathyroid bone disease is possible without a vitamin D3 supplement at an earlier stage of renal failure. Thus, administration of 3 g oral calcium carbonate daily was highly effective in treating secondary hyperparathyroidism in patients with mild to moderate renal failure.