LONG-TERM EFFECTS OF INTERMITTENT ORAL ALPHACALCIDOL, CALCIUM-CARBONATE AND LOW-CALCIUM DIALYSIS (1.25 MMOL L-1) ON SECONDARY HYPERPARATHYROIDISM IN PATIENTS AN CONTINUOUS AMBULATORY PERITONEAL-DIALYSIS

Objectives. (i) To examine the effect of alphacalcidol [1 alpha(OH)D-3 ] given as an oral dose twice weekly in combination with CaCO3 and low -calcium dialysis (1.25 mmol L-1) on the secondary hyperparathyroidism in continuous ambulatory peritoneal dialysis (CAPD). (ii) To examine the changes in peritoneal mass transfer for calcium, phosphorus, magne sium, lactate, creatinine, urea, glucose, pH and albumin after shift t o low-calcium dialysis solution. Design. An open study in patients on CAPD. Setting. Renal division, Rigshospitalet, Copenhagen. Subjects. T hirty-nine patients were included and completed 12 weeks of treatment. Thirty of the patients completed 52 weeks of treatment. A peritoneal equilibrium test (PET) was performed in seven patients. Interventions. Following two sets of blood samples obtained as basal values the calc ium concentration was reduced in the dialysis fluid from 1.75 mmol L-1 to 1.25 mmol L-1. Increasing doses of oral 1 alpha(OH)D-3 were then a dministered under careful control of p-ionized calcium (p-Ca2+) and p- inorganic phosphate (p-P-i). Blood samples were obtained every 2-4 wee ks for 52 weeks. PET was performed using standard dialysis fluid and 1 week later using low-calcium dialysis fluid after a preceding overnig ht dwell. Two litres of glucose 22.7 mg mL(-1) were used. Main outcome measures. Intact parathyroid hormone (PTH), p-Ca2+, p-P-i, doses of C aCO3, doses of 1 alpha(OH)D-3, peritoneal mass transfer for calcium, i norganic phosphate, magnesium, lactate, creatinine, urea, glucose and albumin. Results. Thirty nine patients with initial PTH values 144 +/- 26 pg mL(-1) were followed for 12 weeks and 30 patients for 52 weeks. A negative calcium balance was induced after shifting to low-calcium dialysis fluid. After 2 weeks of treatment a significant increase of P TH by approximately 60% and a small but significant decrease of p-Ca2 was observed. After 12 weeks of treatment with increasing doses of 1 alpha(OH)D-3 and CaCO3, PTH was again reduced to levels not significan tly different from the initial values. After 52 weeks of treatment no deterioration of the secondary hyperparathyroidism was seen. Conclusio ns. A calcium concentration of 1.25 mmol L-1 in the CAPD dialysate mad e it possible to reduce the amount of aluminium-containing phosphate b inder, to increase the doses of CaCO3 and to use pulse oral 1 alpha(OH )D-3 without causing severe hypercalcaemia in the patients. After a sh ort elevation of PTH, the PTH levels remained at normal or near normal levels and the long-term results clearly demonstrated that an aggrava tion of the secondary hyperparathyroidism could be inhibited.