Kim TY, et al. - After oral or intravenous bisphosphonate use, researchers compared changes in bone mineral density (BMD) and procollagen type I N propeptide (PINP). Women who received a mean five years of alendronate were randomized to placebo or continued treatment in the Fracture Intervention Trial Long-term Extension (FLEX). Women who received three years of zoledronic acid were randomized to placebo or continued treatment in the Health Outcomes and Reduced Incidence with Zoledronic Acid Once Yearly-Pivotal Fracture Trial Extension I (HORIZON-PFT E1). The FLEX group had a greater mean total hip BMD decreases and greater rises in PINP after three years of placebo. A considerable proportion of former users of alendronate and zoledronic acid had significant declines in total hip BMD and elevations in PINP three years after discontinuation of bisphosphonate. They considered that alendronate might have a faster drug effect offset than zoledronic acid despite a longer course of treatment.