Keith McCormick's new book "Great Bones" has info on how to transition from Prolia to Reclast. He says that if the Prolia is still active 6 months after your last injection, the Reclast won't work. That means there is potentially a period after that Reclast when you are losing bone via rebound.

But then again, if you wait 9 months after the last Prolia, there could have been a rebound bone loss starting 5 months after that last injection.

People really vary in their response and the length of their response to Prolia, he writes. The drug company (Amgen) suggested Reclast after 6 months from studies but there is variability and timing is important.

He writes that delaying Reclast for even 4-16 weeks after Prolia wears off can increase fracture risk.

DEXA's measure bone density but quality is important too. For that reason he says that repeat CTX tests (every 4-6 weeks) during this period after stopping Prolia are essential to determine when Prolia has worn off, which is when Reclast is then effective and should be started immediately.

Another CTX should be done one month after Reclast, and again 3-6 months after and a repeat infusion should be done if CTX continues to rise meaning continued bone loss.

My doc doesn't do CTX at all. I did have a baseline done, suggested by Dr. McCormick. I imagine this info is right on target but we need docs who will do this!