IMPROVEMENT OF SEVERE SECONDARY HYPERPARATHYROIDISM IN DIALYSIS PATIENTS BY INTRAVENOUS 1-ALPHA(OH) VITAMIN-D3, ORAL CACO3 AND LOW DIALYSATE CALCIUM

Seventeen patients (9 men, 8 women; aged 27 to 75 years) who were on c hronic hemodialysis for 1 to 14 years were included in the study becau se they had severe hyperparathyroidism diagnosed by elevated plasma al kaline phosphatase and on plasma intact PTH levels more than twice the upper limit of normal. They had been previously treated with various combinations of oral calcium and/or Al(OH)3 as phosphate binders, oral 1alpha(OH) vitamin D3 metabolites and a dialysate calcium concentrati on (DCa) of 1.6 to 1.75 mmol/liter. When i.v. alphacalcidol was introd uced DCa was reduced to 1.25 mmol/liter and CaCO3 taken with the meal was used as the sole phosphate binder. alphacalcidol was i.v. injected after the third dialysis of the week at a dose up to 4 mug per dialys is in order to obtain a predialysis plasma concentration of Ca at 2.5 +/- 0.2 and PO4 between 1.5 and 2 mmol/liter. All the other treatments were discontinued. During the six months of follow-up, the mean weekl y dose of alphacalcidol was 6 mug and CaCO3 700 +/- 50 mmol. Plasma ca lcium (P(Ca)) increased moderately from 2.35 to 2.47 mmol/liter (P < 0 .05) whereas plasma PO4 (P(PO4)) did not significantly increase (1.56/ 1.64 mmol/liter). Total alkaline phosphatase and its bone isoenzyme ac tivity decreased significantly to normal values [respectively from 186 to 83 IU (normal: 135) and from 102 to 32 IU (normal < 33)] whereas p lasma intact PTH decreased from 485 to 125 pg/ml (normal < 55). Thus, intermittent i.v. administration of alphacalcidol to hemodialysis pati ents significantly improves, within six months, severe hyperparathyroi dism without hyperphosphatemia. hypercalcemia or aluminium intoxicatio n hazards thanks to the combined use of oral CaCO3 as sole phosphate b inder and a low DCa.