Multicenter clinical trial of 22-oxa-1,25-dihydroxyvitamin D3 for chronic dialysis patients

Conventional calcitriol treatment can suppress parathyroid hormone (PTH) secretion in hemodialysis patients, although it can cause refractory hyperparathyroidism in some patients. We attempted to elucidate clinical outcomes of intravenous 22-oxa-1,25-dihydroxyvitamin D(3) (OCT) treatment and their determinants in a multicenter clinical trial.

One hundred one patients with serum PTH levels greater than 300 pg/mL (300 ng/L) and serum calcium levels less than 11 mg/dL (2.74 mmol/L) were recruited. OCT was administered intravenously at the end of each dialysis session. The dose was decreased by 5 microg when serum PTH level was less than 300 pg/mL or serum calcium level was greater than 11 mg/dL.

OCT was administered for 4.8 months to 101 patients (average age, 55.1 years) who were on dialysis therapy for 15.9 years. Percentages of decrease in PTH levels greater than 30% were obtained in 44 patients (43.5%). These patients were on dialysis therapy for a shorter duration than those who showed less than 30% decreases (13.0 +/- 3.3 versus 17.9 +/- 3.0 years). Multiple regression analysis of the final PTH level or percentage of decrease in PTH level with respect to initial PTH level, serum calcium level, serum phosphate level, age, and dialysis therapy duration showed that determinants of percentages of decrease in PTH levels were initial serum calcium and phosphate levels. Conversely, significant determinants of the final PTH level were initial PTH levels and initial calcium levels.

These results show that the decrease in PTH levels by OCT therapy could be predicted in patients with low calcium, PTH, and alkaline phosphatase levels; high phosphate levels; and short dialysis therapy duration before the start of OCT administration.