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

Purpose: We tested whether UroPhos closed integral-K, a new slow relea se neutral form of potassium phosphate (155 mg. phosphate, 8 mEq. pota ssium per tablet) in a dose of 4 tablets twice daily would produce a s ustained hypocalciuric response and maintain bone mass in patients wit h absorptive hypercalciuria, a major cause of nephrolithiasis characte rized by excessive intestinal calcium absorption accompanied in some p atients by excessive bone loss. Materials and Methods: A total of 25 p atients with absorptive hypercalciuria were studied in a 4-year, prosp ective, open trial with UroPhos-K at yearly intervals during a 4-day i npatient 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 uri nary calcium (264 to 181 mg. daily). Fractional (47)calcium absorption decreased modestly (74.0 to 64.6%) commensurate with a reduction in s erum 1,25-dihydroxyvitamin D (42 to 34 pg./ml.). Intact parathyroid ho rmone increased within the normal range (30 to 42 pg./ml.). Bone miner al density was stable at the lumbar spine, femoral neck and distal thi rd of the radius. Conclusions: UroPhos-K may provide a long-term alter native for hypercalciuric patients in whom thiazide therapy fails.