Objective: To compare the hypocalciuric and potential side-effects of hydrochlorothiazide (HCT) to indapamide (IND; a thiazide-like drug) in patients with idiopathic hypercalciuria.
Patients, subjects and methods: Twelve patients with recurrent renal calculi and renal hypercalciuria were studied using a randomized double-blind cross-over protocol. In addition, because the side-effects of HCT are attenuated using small doses, the hypocalciuric effect of 12.5, 25 and 50 mg daily was assessed in six normal subjects.
Results: There was a significant reduction in urinary calcium excretion using both agents, with a mean (SD) of 6.06 (2.68) and 3.37 (2.00) mmol/24 h using IND, and 5.58 (1.98) and 3.93 (2.35) mmol/24 h using HCT, before and after treatment (P < 0.05). The treatment was not sufficiently prolonged to assess adequately all the side-effects of either agent but both produced a similar decrease in serum potassium, whilst HCT significantly increased the mean (SD) serum urate levels, from 0.34 (0.09) to 0.43 (0.08) mmol/L (P < 0.01). There was also a significant decrease in mean (SD) urinary citrate excretion in those receiving HCT, from 1.41 (1.05) to 1.00 (0.71) mmol/24 h (P < 0.001), but not in those receiving IND, from 1.19 (0.71) to 1.18 (0.79) mmol/24 h. Although there was a hypocalciuric effect with doses of 12.5 and 25 mg HCT, it was sub-therapeutic when compared with the dose of 50 mg.
Conclusion: At a daily dose of 2.5 mg, IND is at least as effective as 50 mg HCT in controlling hypercalciuria. Because of its safety profile and lack of effects on urinary citrate excretion, this agent should be the preferred therapy for patients with idiopathic hypercalciuria and recurrent renal calculi.