Alendronate, risedronate, ibandronate, and zoledronic acid belong to which drug class?

• A. Bisphosphonates
• B. Selective estrogen receptor modulators
• C. Denosumab
• D. Calcitonin

Answer: (A)

These drugs are antiresorptives used to treat osteoporosis, specifically the class known as bisphosphonates. The four agents listed are nitrogen-containing bisphosphonates, which have a strong affinity for bone mineral and are incorporated into the bone matrix. When osteoclasts resorb bone, they take up the drug and it disrupts the mevalonate pathway by inhibiting farnesyl pyrophosphate synthase. This prevents prenylation of signaling proteins, causing osteoclast dysfunction and apoptosis, which reduces bone resorption and helps increase bone density over time.

Other drug classes in this realm work differently. SERMs modulate estrogen receptors to reduce bone loss, denosumab is a monoclonal antibody that blocks RANKL to inhibit osteoclast formation, and calcitonin directly inhibits osteoclast activity via a different mechanism.