Clinical use of bisphosphonates.

The bisphosphonates (formerly known as diphosphonates) constitute a recently developed class of drugs for use in a variety of diseases of bone and calcium metabolism. Developed in the past three decades, only a few compounds of this large family of drugs are now commercially available for various therapeutic indications that vary broadly, from country to country. The clinical use of bisphosphonates is based on their ability to inhibit bone resorption. Thus, their main indications concern diseases with high bone remodeling, such as Paget's disease of bone, osteoporosis, metastatic bone diseases, and malignant and nonmalignant hypercalcemia. Their other main action is to inhibit bone formation; the ratio of inhibition of bone resorption to inhibition of bone formation varies according to the compounds. This ratio is less favorable for the first available bisphosphonates, such as etidronate. New bisphosphonates are more and more potent and possess a safer ratio. With their increasing power, there could be some risk of freezing bone remodeling, but so far this fearful complication has not yet been observed.