Bisphosphonates

Introduction

• Definition — Synthetic, non-hydrolysable analogues of inorganic pyrophosphate in which the central O of the P–O–P backbone is replaced by carbon, giving a stable P–C–P ('geminal') structure.
• Class identity — The most potent and most widely used antiresorptive drugs; selectively inhibit osteoclast-mediated bone resorption.
• Anti-catabolic, not anabolic — Slow bone loss rather than build bone — BMD rises over the first ~12–18 months (filling of the remodeling space) then plateaus.
• Core uses — First-line for osteoporosis (postmenopausal, male, glucocorticoid-induced), Paget disease, hypercalcaemia of malignancy, and osteolytic metastases / multiple myeloma.