CALCITRIOL ORAL-THERAPY FOR THE PREVENTION OF SECONDARY HYPERPARATHYROIDISM IN PATIENTS WITH PREDIALYTIC RENAL-FAILURE

Secondary hyperparathyroidism is a common feature of chronic renal fai lure and vitamin D deficiency plays an important role in the developme nt of this abnormality. Several therapeutical calcitriol schedules hav e been used in treating uremic hyperparathyroidism but recently oral b oluses have been proposed as more effective. In this study we compare the efficacy of three different oral calcitriol regimens in suppressin g iPTH secretion in predialytic chronic renal failure. Sixteen (16) pa tients (mean age 51 +/- 16 years; creatinine clearance 22.9 +/- 9.8 mi ; range 8-32 ml/min) were treated in a cross-over randomized design wi th oral daily calcitriol 0.5 mu g/die (Treatment A), three oral boluse s of 2 mu g Of calcitriol a week (Treatment B) and a single oral bolus of 2 mu g of calcitriol a week (Treatment C). All treatment periods l asted three months and were followed by a wash-out period of one month . Serum iPTH (Allegro Nichols), 1-25 vitamin D (IRMA-MAB), total and i onized calcium (Nova 8 Pabish), serum phosphate, alkaline phosphatase and creatinine clearance were measured every two weeks. Serum iPTH was also determined in a control group of fifteen (15) patients (mean age 47 +/- 12 years, creatinine clearances of 21 +/- 12 mi/min) observed for three months without calcitriol treatment, Daily oral intake of 0. 5 mu g of calcitriol prevents an increase of iPTH without causing hype rcalcemia, but only oral boluses (B and C) decreased iPTH: from 270 +/ - 169 pg/ml to 135 +/- 76 pg/ml (p <0.01; B) and to 165 +/- 121 pg/ml (p <0.05; C). Serum iPTH increased from 293 +/- 121 to 323 +/- 129 pg/ ml (p = n. s.). No significant differences in renal function were obse rved during the different study periods. Our results confirm the good efficacy of multiple calcitriol oral boluses but also suggest for the first time a single weekly bolus as a reliable approach to the treatme nt of secondary hyperparathyroidism in pre-dialytic renal failure.