Physiological effects of slow release potassium phosphate for absorptive hypercalciuria: a randomized double-blind trial.

Abstract

We examined the physiological effects and tolerance of UroPhos-K, a slow release neutral form of potassium phosphate (155 mg. phosphate and 8 mEq. potassium per tablet) in patients with absorptive hypercalciuria. A total of 31 patients with absorptive hypercalciuria were studied at baseline and after 3 months of treatment with 4 tablets twice daily of UroPhos-K or placebo (identical in appearance) in a prospective randomized, placebo controlled, double-blind trial during a 4-day inpatient study with a daily constant metabolic diet containing 400 mg. calcium, 100 mEq. sodium and 800 mg. phosphate. Treatment with UroPhos-K did not cause significant gastrointestinal side effects, increase fasting serum potassium or phosphorus, or reduce hemoglobin or creatinine clearance. It reduced urinary calcium excretion from 277 +/- 72 to 166 +/- 43 mg. per day (p < 0.001), associated with a reduction in serum 1,25-dihydroxyvitamin D concentration from 50 +/- 11 to 42 +/- 9 pg./ml. (p < 0.001). Indexes of intestinal calcium absorption and markers of bone turnover also decreased modestly. None of these changes was seen in the placebo group. In patients with absorptive hypercalciuria UroPhos-K seems to correct hypercalciuria by a combination of reduced intestinal absorption, bone resorption and improved renal calcium reabsorption. The drug is well tolerated compared to placebo.