Background: The role of bisphosphonates (BPs) in the management of patients with hypercalciuria (HC) associated with osteoporosis is still uncertain. The aim of the study was to evaluate the effect of alendronate and indapamide alone or in combination on bone mineral density (BMD) and 24-h urinary calcium excretion (24-CaU) in post-menopausal women with HC and low BMD.
Methods: A total of 77 post-menopausal women with HC (24-CaU > 4 mg/kg/day) and low BMD [T-score < -2.0 at lumbar spine (LS), femoral neck (FN) or total hip (TH)] from two centres of Northern Italy were randomized to receive indapamide 2.5 mg daily alone (24 patients, IND group), alendronate 70 mg weekly alone (27 patients, ALN group) or the combination therapy (26 patients, ALN + IND group). Throughout the study, all subjects received daily calcium supplements, depending on their dietary intake, to maintain a daily input of 1000 mg. Patients were instructed to increase water intake up to 2000 mL daily. The percentage and absolute changes of BMD at LS, FN and TH, and the variation of 24-CaU from baseline at 1 year were the primary outcomes. Serum calcium, phosphate, parathyroid hormone and bone alkaline phosphatase were also measured.
Results: Overall 67 women completed the study and were included in the final analysis. Patients in the three groups were similar with regard to baseline characteristics. BMD did not significantly change from baseline after 1 year of treatment with indapamide (LS: +1 +/- 3.1%; FN: -0.3 +/- 3.5%; TH: -0.4 +/- 3.1%), while it showed a significant increase from baseline in the other two groups (ALN; LS: +5.8 +/- 4.2%, P < 0.001; FN: +3.9 +/- 7.9%, P = 0.018; TH: +2 +/- 3.6%, P = 0.006) (ALN + IND; LS: +8.2 +/- 5.3%, P < 0.001; FN: +4.9 +/- 6.7%, P = 0.007; TH: +2.9 +/- 4.2%, P = 0.004). Patients in the combination group showed a significantly higher increase of BMD at LS compared to ALN (P = 0.04). After 1 year, 24-CaU values significantly decreased from baseline in all groups (IND, 239 +/- 78 versus 364 +/- 44, P < 0.001) (ALN, 279 +/- 68 versus 379 +/- 79, P < 0.001) (ALN + IND, 191 +/- 68 versus 390 +/- 55, P < 0.001). The mean percentage decrease of 24-CaU in ALN + IND group (-50%) was significantly greater compared to ALN (-24%, P < 0.001) and IND (-35%, P = 0.012).
Conclusions: These results show a benefit, in terms of BMD improvement and 24-CaU reduction, associated with BPs' therapy in combination with indapamide in HC associated with osteoporosis. The combination therapy demonstrated a reduction of 24-CaU and an increase in LS BMD superior to that observed with alendronate alone. Our results support a new potential approach with BPs associated with thiazide diuretics or indapamide in the management of post-menopausal women with HC and associated bone loss. Studies on the larger sample size are needed to demonstrate the efficacy on the fracture outcome.