<qa>  What is the first dose of active zoledronic acid?This study is a randomized, double-blind, placebo-controlled 2-year study. Participants will receive one dose of active zoledronic acid during the first month after heart or liver transplantation and weekly placebo alendronate pills or one dose of placebo zoledronic acid and weekly active alendronate pills for the first year after transplant. Over 2 years, participants will provide blood samples on nine occasions. Bone density will be performed 4-5 times and spine xrays will be performed twice. 