Carr A, Kerr SJ, Richardson R, et al. - Researchers wanted to see if zoledronic acid (ZOL)'s effects would endure without further infusions, so changes in left hip vs spine bone mineral density (BMD) were assessed over 36 months in patients randomly allocated to ZOL 5 mg at baseline and month 12 (and continuing tenofovir disoproxil fumarate [TDF]) or switching to TDF (without receiving ZOL). In addition, they assessed if changes in C-terminal telopeptide of type 1 collagen (CTX; bone resorption) and procollagen type 1 N propeptide (P1NP; bone formation) at month 3 forecast BMD changes at month 36. The per-protocol populations included 32 of 43 candidates randomized to ZOL and 37 of 42 candidates who switched TDF. Mean baseline hip and spine BMD change was stable and stayed greater at month 36 with ZOL vs TDF switching, even without getting ZOL after month 12. In both groups, CTX and P1NP levels decreased, but did so with ZOL significantly more. Only percent changes in P1NP at month 3 were inversely associated with changes in BMD at month 36. Continuous increases in BMD through month 36 resulted from two ZOL infusions (along with continuing TDF), and these stayed greater vs TDF switching.