We will enroll patients who have undergone cardiac transplantation into a randomized, double-blind, 12-month study of the efficacy and safety of calcitriol (Rocaltrol) and alendronate sodium (Fosamax) in the prevention of bone loss after transplantation. We will give all participants standard pre- and post-transplantation management and immunosuppressive therapy, three tablets of calcium citrate (Citracal + D, each containing 315 mg of elemental calcium and 200 IU of vitamin D), and a multivitamin providing 400 units of vitamin D daily. We will randomize participants to one of two active treatment groups within 1 month of transplantation. We will give Group A active alendronate (10 mg/day) and placebo calcitriol. We will give Group B placebo alendronate and active calcitriol (0.25 micrograms BID). The primary efficacy endpoint is the change in spine bone mineral density (BMD) during the first 6 months after transplantation. The secondary efficacy endpoint is the change in hip BMD during the first year after transplantation. We will also monitor the incidence of vertebral fracture.

We will invite eligible subjects to participate in the study. We will offer patients who elect not to participate in the therapeutic trial the opportunity to have serial BMD measurements at the same intervals as treated subjects and to be followed as untreated controls. We will continue recruitment until we have randomized a total of 146 cardiac transplant recipients. We will perform bone densitometry at randomization (unless performed within the previous month) and at 6 and 12 months. We will obtain radiographs (x-rays) at randomization and will repeat them at 12 months to detect undiagnosed vertebral fractures.