Clinical experience with long-term bendroflumethiazide treatment in calcium oxalate stone formers.

Bendroflumethiazide was administered to 85 patients (62 men, 23 women) with recurrent calcium oxalate stone disease. Side effects leading to interrupted treatment were observed in 26 (31%) of the patients. Fifty-nine (40 men, 19 women) remained on treatment for a mean (+/- SD) period of 3.7 +/- 1.0 years, and 21 reported late side effects. Twenty patients were given 2.5 mg bendroflumethiazide daily (Group A), 27 were given 2.5 mg twice daily (Group B), and 12 were given 5 mg once daily (Group C). Eight patients (14%) formed new stones and another two demonstrated stone growth during treatment. A beneficial effect on stone formation was observed in Groups B and C but not in Group A. Patients who failed to respond to treatment had a pre-treatment stone formation rate of 0.74 stones per year compared with 0.22 in those who did not form new stones. Those with recurrence during treatment had a lower citrate excretion than other patients. No effect on urinary citrate was recorded during treatment, and long-term treatment with bendroflumethiazide did not affect oxalate excretion.