Effect of calcitriol on bone loss after cardiac or lung transplantation

Rapid bone loss after cardiac and lung transplantation results in an increa sed risk of osteoporotic fracture. This study examined the efficacy of trea tment with calcitriol (1,25-dihydroxyvitamin D-3) in preventing bone loss i n patients undergoing cardiac or lung transplantation, In this 2-year doubl e-blind, stratified study, 65 patients undergoing cardiac or single lung tr ansplantation were randomly allocated to receive either placebo or calcitri ol (0.5-0.75 mu g/day), the latter for either 12 months or 24 months. All p atients received 600 mg calcium/day. Bone mineral density (BMD) was measure d every 6 months for 2 years by dual-energy X-ray absorptiometry. There was no significant difference between groups with respect to age or cumulative dose of prednis(ol)one or cyclosporine over the 2 Sears. Bone loss at the proximal femur was significantly reduced or prevented at all three sites by treatment with calcitriol for 2 Sears compared with treatment with calcium alone. Treatment with calcitriol for 12 months followed by calcium for 12 months resulted in similar proximal femoral bone loss to that seen in those patients treated with calcium for 24 months, suggesting calcitriol prophyl axis needs to be continued beyond 12 months. At the lumbar spine, there wer e no significant differences in BMD between groups. Over a period of 2 year s, 22 new vertebral fractures/deformities occurred in it patients treated w ith calcium alone compared with one new vertebral fracture in 1 patient tre ated with calcitriol, Because the sample size was too low to provide reliab le interpretation of vertebral fracture rates, this difference is likely a chance result. Mild hypercalcemia was common with calcitriol therapy, as wa s mild hypercalciuria (59% of patients vs. 10% controls), but there were no significant differences between groups in serum creatinine after 2 years. These data suggest calcitriol has a role in reducing proximal femur bone lo ss after cardiac or lung transplantation but treatment needs to be continue d beyond 1 gear.