SUSTAINED REDUCTION IN URINARY CALCIUM DURING LONG-TERM TREATMENT WITH SLOW RELEASE NEUTRAL POTASSIUM PHOSPHATE IN ABSORPTIVE HYPERCALCIURIA

Purpose

We tested whether UroPhos^§-K a new slow release neutral form of potassium phosphate (155 mg. phosphate, 8 mEq. potassium per tablet) in a dose of 4 tablets twice daily absorptive hypercalciuria, a major cause of nephrolithiasis characterized by excessive intestinal calcium absorption accompanied in some patients by excessive bone loss.

Materials and Methods

A total of 25 patients with absorptive hypercalciuria were studied in a 4-year, prospective, open trial with UroPhos-K at yearly intervals during a 4-day inpatient physiological study with a constant metabolic diet containing 400 mg. calcium, 100 mEq. sodium and 800 mg. phosphate daily.

Results

Treatment with UroPhos-K caused a sustained, marked reduction in urinary calcium (264 to 181 mg. daily). Fractional⁴⁷ calcium absorption decreased modestly (74.0 to 64.6%) commensurate with a reduction in serum 1,25-dihydroxyvitamin D (42 to 34 pg./ml.). Intact parathyroid hormone increased within the normal range (30 to 42 pg./ml.). Bone mineral density was stable at the lumbar spine, femoral neck and distal third of the radius.

Conclusions

UroPhos-K may provide a long-term alternative for hypercalciuric patients in whom thiazide therapy fails.