Calcium balance during pulse alfacalcidol therapy for secondary hyperparathyroidism in CAPD patients treated with 1.0 and 1.25 mmol/L dialysate calcium

Hypercalcemia frequently occurs in continuous ambulatory peritoneal dialysis (CAPD) patients treated with calcium carbonate and vitamin D metabolites. To reduce the incidence of this complication, it has been proposed to use dialysate solutions with a low calcium concentration. However, there is concern that these solutions may lead to a negative calcium balance. We measured calcium balance in 13 CAPD patients with secondary hyperparathyroidism who were treated with calcium carbonate and alfacalcidol, 2 μg twice weekly, while using 1.0- (1.0 group) and 1.25-mmol/L (1.25 group) dialysate calcium solutions. Calcium absorption was measured after the administration of Ca⁴⁷. Results for the 1.0 (n = 6) and 1.25 (n = 7) groups included fractional calcium absorptions of 0.14 (range, 0.09 to 0.27) and 0.08 (range, 0.03 to 0.40; P = not significant [NS]) and calcium absorptions of 380 ± 92 and 331 ± 83 mg/d (P = NS). Dialysate calcium losses were 93 ± 20 and 91 ± 26 mg/d, and total calcium losses (dialysate and urine) were 106 ± 16 and 108 ± 40 mg/d (P = NS). Calcium balance was positive in all patients (274 ± 92 and 223 ± 65 mg/d; P = NS). These data suggest that the use of 1.0- and 1.25-mmol/L calcium solutions in conjunction with calcium carbonate and pulse alfacalcidol therapy is associated with a positive calcium balance in CAPD patients.