Among these, zoledronic acid is recommended as first-line therapy for Paget disease of bone in professional guidelines (1, 2), whereas other amino-bisphosphonates (such as alendronate, risedronate, and pamidronate) are 2nd-line, and the simple bisphosphonates (bisphosphonates without an extra nitrogen atom, such as tiludronate and etidronate) are 3rd-line therapy.