Switching From Oral Bisphosphonates to Bazedoxifene to Evaluate Effects on Bone Mineral Density in Postmenopausal Women

Inclusion Criteria: * Ambulatory postmenopausal women 55 years or older at screening * Have received daily, weekly or monthly oral bisphosphonates at least for 3 years and treatment change is indicated (not responses to bisphosphonates, for bad tolerability or for the potential risk of side effects in a long term treatment with bisphosphonates-indicated by Federal Drug Administration, European Medicines Agency. * Subjects has stop bisphosphonates therapy no more than one month before screening visit for subjects in daily or weekly bisphosphonates * Subjects has stop bisphosphonates therapy no more than two months before screening visit for subjects in monthly bisphosphonates * Screening T-score at the lumbar spine ≤ -2.0 to -4.0 by Dual X ray Absorptiometry (DXA) scan * At least 2 lumbar vertebrae must be evaluable by DXA * Al least one hip must be evaluable by DXA (for secondary objectives) Exclusion Criteria: * Any disorder that compromises the ability of the subject to give written informed consent and/or to comply with study procedures * Current use of medication prescribed for osteoporosis other than oral bisphosphonates * Subjects who had received intravenous bisphosphonates or fluoride (except for dental treatment) * Subjects who had received any Selective Estrogens Receptor Modulator (SERM), anabolic steroids, systemic hormone replacement, calcitonin or calcitriol within 3 months. * Subjects who had received strontium ranelate, parathyroid hormone (PTH) or PTH derivates within 1 year. * Hyper or hypothyroidism, current hyper or hypoparathyroidism * History of Venous Thromboembolism Event (VTE) * Significantly impaired renal function as determined by estimated Glomerular Filtration Rate less 35 mL/min * Hyper or hypocalcemia * Vitamin D deficiency (serum 25 (OH) vit D level \< 20 ng/mL (\< 50nmol/L) * Any condition that could result in impaired calcium metabolism or metabolic bone disease that could interfere with interpretation findings