Bisphosphonates are structural analogues of inorganic pyrophosphate, where the oxygen atom has been substituted by a carbon atom. Differences in the R2 side-chain bound to the carbon atom and the nitrogen group determine their variations in duration of action, bone affinity and anti-fracture efficacy [1,2]. Bisphosphonates inhibit enzymes involved in osteoclastic activity, and thus suppress bone resorption [1,2]. The main bisphosphonates are alendronate, risedronate, ibandronate and zoledronic acid, which constitute the first-line therapeutic agents in both postmenopausal and male osteoporosis, as they have well-documented anti-fracture efficacy [1,2].
