PULSE ORAL CALCITRIOL FOR THE TREATMENT OF HYPERPARATHYROIDISM IN PATIENTS ON CONTINUOUS AMBULATORY PERITONEAL-DIALYSIS - PRELIMINARY-OBSERVATIONS

A direct effect of calcitriol on the regulation of the secretion of parathyroid hormone (PTH) has been shown in vitro and in vivo. In patients with renal failure on maintenance hemodialysis, it has been shown that intravenous (IV) administration of calcitriol appears to be superior to continuous oral administration. This may be due to the higher levels of calcitriol obtained in blood with consequent improved delivery of calcitriol to peripheral target tissues including the parathyroid glands. However, IV administration of calcitriol, is not practical for patients with end-stage renal disease (ESRD) who are maintained on continuous ambulatory peritoneal dialysis (CAPO). The present studies were designed to investigate whether intermittent administration of large doses of calcitriol orally (“pulse therapy”) could mimic the effects of IV calcitriol in hemodialysis patients and achieve suppression of PTH secretion. Studies were performed in five patients who had been maintained on CAPO for more than 6 months. After basal determinations of calcium, phosphorus, and PTH, therapy was begun with calcitriol administered orally in a dose of 5 δg given twice per week. Calcium carbonate was continued as a phosphate binder. Dialysate calcium concentration was 1.75 mmol/L (3.5 mEq/L). With this therapy, PTH levels decreased rapidly, and, after 4 to 6 weeks of therapy, reached values 60% lower than pretreatment values. Mean values for serum calcium did not change significantly (2.29 ± 0.12 mmol/L [9.6 ± 0.5 mg/dL] before treatment compared with 2.32 ± 0.08 mmol/L [9.7 ± 0.25 mg/dL] after therapy). Mean serum phosphorus was also unchanged. These data indicate that in these short-term studies, intermittent pulse therapy with calcitriol, administered orally, was well tolerated and resuHed in substantial suppression of PTH secretion. This mode of therapy may be advantageous for the control of hyperparathyroidism in patients on CAPD. © 1992, National Kidney Foundation. All rights reserved.. All rights reserved.