PROTOCOL ENTRY CRITERIA:

--Disease Characteristics-- Absorptive hypercalciuria Intestinal hyperabsorption of calcium, i.e.: Exaggerated calciuric response to oral calcium load OR Fractional calcium-47 absorption greater than 0.61 Calciuria greater than 200 mg/day on random and calcium-restricted diet Normal or high fasting urinary calcium Normal serum calcium Normal serum parathyroid hormone No primary hyperparathyroidism At least 1 calcium oxalate stone within the past 3 years No struvite or carbonate apatite stones No noncalcareous stones No numerous stones making precise quantitation difficult No renal tubular acidosis --Prior/Concurrent Therapy-- No concurrent drug therapy for nephrolithiasis --Patient Characteristics-- Creatinine clearance at least 0.7 mL/min per kilogram No hyperkalemia No hyperphosphatemia No urinary tract infection Other: No predisposition to hyperkalemia, including concurrent use of the following drugs: Potassium-sparing diuretics Angiotensin-converting enzyme inhibitors Nonsteroidal anti-inflammatory drugs No active peptic ulcer disease No chronic diarrhea

History of severe allergic reactions to study medication Currently pregnant or breastfeeding Recent participation in another clinical trial within the last 30 days Presence of uncontrolled medical conditions that could affect safety