Bisphosphonates such as alendronate (Fosamax, Merck) and pamidronate (Aredia, Ciba–Geigy) are synthetic analogues of inorganic pyrophosphate. The main effect of bisphosphonates, which are deposited on the surface of bone and ingested by osteoclasts during bone turnover, is antiresorptive. They inhibit the mevalonate pathway in osteoclasts, enhancing apoptosis and inhibiting skeleton resorption. In adults, bisphosphonates are largely used to treat osteoporosis, although Paget's disease, metastatic breast carcinoma, and hyperparathyroidism are also indications for treatment.The use of bisphosphonates, particularly intravenous pamidronate, has been extended to children through off-label use for osteoporotic or lytic bone conditions, including osteogenesis imperfecta, fibrous dysplasia, juvenile . . .