The Comparison of Ibandronate and Zoledronic Acid After Denosumab Discontinuation

This study is a prospective, multicenter, open-label, randomized non-inferiority trial comparing intravenous ibandronate and zoledronic acid as sequential therapy after denosumab discontinuation in postmenopausal women with osteoporosis. This trial primarily targets patients with short-term denosumab exposure (less than three years) and is conducted as a preliminary investigation. The findings are expected to provide foundational evidence to inform the design of future studies assessing sequential therapies following longer-term denosumab treatment.

Inclusion Criteria: 1. Postmenopausal women aged 50 to 85 years. 2. BMD T-score ≤ -1.5 and \> -3.0 at the lumbar spine or total hip. 3. Regular treatment with denosumab administered every 6 months for at least 1 year and less than 3 years (3 to 5 doses). 4. Physically and mentally capable of understanding and complying with the study protocol and follow-up. 5. Signed informed consent. Exclusion Criteria: 1. History of fragility or osteoporotic fracture within the past 12 months. 2. Current or prior treatment within the past 12 months with osteoporosis medications other than denosumab, including Romosozumab, Teriparatide, Alendronate, Ibandronate, Zoledronic acid, Risedronate and Raloxifene. 3. Allergy to bisphosphonates. 4. Secondary osteoporosis. 5. Metabolic bone diseases. 6. Any autoimmune disease. 7. Requirement for long-term use of medications known to affect bone metabolism (e.g., systemic glucocorticoids or hormone therapy). 8. Primary or metastatic bone tumors. 9. Cancer patients, except for in situ carcinoma and non-melanoma skin cancer, unless fully treated and in remission for five years. 10. Hypocalcemia. 11. Vitamin D deficiency (serum 25-hydroxyvitamin D \< 25 ng/mL). 12. Renal disease (eGFR \< 35 mL/min/1.73 m²) or dialysis patients. 13. Planned dental procedures (e.g., extractions, implants) within the next year. 14. Smoking more than one pack per day (except for those who have quit for over ten years).