Diurnal variation of urine composition in calcium oxalate stone disease during treatment with bendroflumethiazide.

Urine samples, collected hourly between 6.00 and 23.00 h and in one single night fraction, were analyzed for calcium (Ca) and magnesium (Mg) before and during daily administration of 5 mg bendroflumethiazide to 13 Ca-oxalate (CaOx) stone formers. In some of them urinary oxalate (Ox), citrate and sodium were analyzed as well. Bendroflumethiazide was administered in divided doses to 7 and in a single dose to 6 patients. After 4-8 weeks of treatment urinary Ca decreased by approximately 25% in both groups and the reduction was evenly distributed over the day. The reduction of the Ca/Mg quotient and the CaOx risk index was most pronounced following meals. The AP(CaOx) index, an estimate of the CaOx ion activity product, was favorably reduced. No important differences were recorded for the different types of bendroflumethiazide administration and thus one single dose might be equally as efficient as two divided doses.