High-dose oral calcitriol and zero calcium peritoneal solutions in CAPD patients with refractory secondary hyperparathyroidism.

We evaluated the effect of pulse oral calcitriol (4 micrograms three times weekly for 6 months) on parathyroid function in nine CAPD patients with hyperparathyroidism refractory to conventional low-dose oral calcitriol. Zero calcium peritoneal solutions were used to prevent the development of hypercalcaemia. The peritoneal loss of calcium increased from 168 +/- 40 to 417 +/- 48 mg/day using zero calcium solutions. Pulse oral calcitriol resulted in a significant decrease in PTH (from 617 +/- 272 to 382 +/- 299 pg/ml) by the 15th day of therapy, while serum iCa did not change from baseline. During the first month of therapy the mean PTH levels remained significantly reduced compared to baseline, thereafter PTH increased in four of nine patients. Hyperphosphataemia was not satisfactorily controlled in four patients, despite large amounts of binders used; seven of nine patients developed hypercalcaemia and required either the substitution of calcium acetate for calcium carbonate or reduction of calcitriol dose. Three patients showed a progressive increase in PTH. In conclusion our data suggest that in most CAPD patients with severe hyperparathyroidism oral calcitriol pulse therapy is not effective in maintaining a permanent suppression in PTH levels.