Compare the data obtained with two formulations of alendronate 70 mg (tablets vs effervescent tablet for buffered solution) on the change in bone turnover markers, on gastric tolerance and on treatment adherence (including compliance and persistence).

Inclusion Criteria:

• Post-menopausal women (at least 5 years after natural / surgical menopause).
• Patients on treatment with alendronate 70mg tablets or alendronate 70mg effervescent tablets for 6-8 months and who will be continued to be treated for a minimum of 12 months.
• Available BTMs (s-CTX), biochemistry (calcium, phosphate, 25-OH vit D, PTH, creatinine) and DXA (lumbar spine, total hip and femoral neck) at the initiation of the treatment.
• Ability to sign an informed patient consent

Exclusion Criteria:

• Patients who had received a prior osteoporosis treatment with anti-resorptive drugs (bisphosphonate or denosumab) or teriparatide before starting alendronate 70 mg.
• Any secondary cause of osteoporosis including current treatment with glucocorticoids or aromatase inhibitors, inflammatory disorders, malabsorption
• Metabolic or cancer bone disease
• Contra-indications to bisphosphonates according to product labelling
• Known or suspected allergy to study product(s) or related products
• Inability to sign an informed consent
• Previous participation in this study

Post-menopausal women with osteoporosis, on treatment with Fosamax® or Binosto® for 6-8 months and who will be continued to be treated for a minimum of 12 months, with available BTMs, biochemistry and DXA at the initiation are to be offered participation in the study at the discretion of the treating physician.