Effects of bendroflumethiazide on bone mineral density; results from the BONATHIAD randomized double-blind placebo-controlled cohort study

Purpose: Thiazide diuretics (TD) may play a role in preventing osteoporosis. The objective was to investigate the effects of bendroflumethiazide in combination with bisphosphonates on bone mineral density, selected blood parameters, blood pressure, pulse, and muscle function. Methods: Double-blinded, randomized, placebo-controlled interventional study in postmenopausal osteoporotic women over the age of 50 years consisting of four arms: 1) 24 weeks with bendroflumethiazide +24 weeks of washout, 2) 24 weeks with placebo +24 weeks of washout, 3) 48 weeks with bendroflumethiazide, or 4) 48 weeks with placebo. At inclusion, participants were on oral bisphosphonates. Intervention consisted of either bendroflumethiazide or placebo. Dual energy X-ray absorptiometry (DXA), vertebral fracture assessment (VFA), quantitative CT (QCT) and selected blood parameters were acquired at baseline and at 48 weeks and Timed-Up-and-Go, handgrip strength, blood pressure, pulse and balance additionally at 24 weeks. Results: 139 postmenopausal Caucasian women over 50 years were randomized (mean age 64.7 years (SEM 0.6, range 51-79)). 109 (78%) completed the study. No difference in the effect of bendroflumethiazide on DXA, VFA, QCT, biochemistry or muscle function were found between the treatment arms. Conclusion: Bendroflumethiazide for 24- or 48 weeks in combination with bisphosphonates does not improve bone mineral density, selected blood parameters or muscle function compared to placebo combined with bisphosphonates. Studies with longer treatment periods and more patients are needed to further characterize the effects of bendroflumethiazide on bone and subpopulations that might benefit from the treatment.