Pharmacology · single question
What is the mechanism of action of bisphosphonates?
Show answer and explanation
Correct answer: A. Inhibit osteoclast function
- A. Bisphosphonates (alendronate, zoledronic acid, ibandronate) work by INHIBITING OSTEOCLAST FUNCTION. They are taken up by osteoclasts during bone resorption and interfere with the mevalonate pathway (inhibiting farnesyl pyrophosphate synthase), preventing osteoclast activation, function, and survival. The result: reduced bone resorption → increased bone density. Dental implication: MRONJ risk from impaired osteoclast-mediated bone remodeling.
- B. Bisphosphonates primarily target osteoclasts — they do not directly stimulate osteoblasts. Teriparatide (parathyroid hormone analog) stimulates osteoblasts.
- C. RANKL blockade is the mechanism of denosumab (Prolia) — a monoclonal antibody that prevents RANKL from activating osteoclasts. Bisphosphonates work differently, inhibiting osteoclast intracellular pathways.
- D. Calcium absorption is enhanced by Vitamin D and parathyroid hormone — not bisphosphonates.