Prolia (denosumab) and Reclast (zoledronic acid) are injections that can be used to treat or prevent osteoporosis in postmenopausal women. But they each work differently because Prolia is a monoclonal antibody (it may also be called a miscellaneous bone resorption agent) and Reclast is a bisphosphonate which means they have different side effects, other uses, tolerability, and effectiveness profiles. Both are prescription medicines.