Normal bone growth and remodeling entail a tightly coupled process of bone resorption and new bone formation. Osteoporosis-related bone loss occurs when bone resorption exceeds bone formation; bisphosphonates decrease bone resorption, thereby slowing bone loss. The pharmacology of bisphosphonates is complex. During therapy, bisphosphonates are incorporated into newly formed bone and can persist there for years, through multiple cycles of bone resorption and deposition. Thus, patients continue to be exposed to the pharmacologic effects of bisphosphonate activity long after they stop taking the medication.