@gravity3 You’re right to wonder about using Fosamax again after 5 years of prior exposure. In my view, Reclast is essentially equivalent to additional years on Fosamax in terms of bisphosphonate exposure at this point, but it’s always best to confirm with your endocrinologist.

In your case, your prior Fosamax use and ongoing HRT both could help lower rebound risk after stopping Prolia. The decision really comes down to balancing total bisphosphonate exposure, residual effect, HRT coverage, dosing flexibility, and practical factors - Reclast works quickly and reliably with a single infusion, while Fosamax takes longer to reach full effect and depends on how well it’s absorbed.

It’s worth bringing up the idea of monitoring CTX, since it can help confirm that the transition is going smoothly. And in case Fosamax alone isn’t enough, Reclast can always be used as a backup.