Effects of once-weekly oral alendronate on bone in children on glucocorticoid treatment

Abstract

Objectives: To determine the effects of once-weekly oral alendronate on indices of bone size, density and resorption in children with chronic illness being treated with glucocorticoids.

Methods: Twenty-two children with chronic illness treated with prednisone were randomized to receive 1 year's treatment with either once-weekly oral placebo or alendronate (1-2 mg/kg body weight) in a double-blind study. The main outcome measures were changes in lumbar spine and femoral shaft size and volumetric density (measured by dual energy X-ray absorptiometry) and N-telopeptide excretion (a marker of bone resorption).

Results: Once-weekly alendronate was well tolerated, and there were no major adverse events. In both groups bone size and bone mineral content increased through growth. Volumetric bone density of the lumbar spine increased significantly in the alendronate group (P = 0.013), but not in the placebo group. There were no differences between the groups in growth in the cortical width of the femoral shaft, but the cross-sectional moment of inertia per unit length-a derived estimate of mechanical strength-increased significantly in the alendronate group (P = 0.014) but not in the placebo group. Urine N-telopeptide excretion was suppressed significantly in the alendronate group (P = 0.007) but not in the placebo group. Height velocity was positively correlated with changes in both lumbar spine area and the total width of the femoral shaft (P = 0.015, P = 0.026, respectively).

Conclusion: Once-weekly oral alendronate is well tolerated, suppresses bone resorption and may improve volumetric bone density at the lumbar spine and mechanical strength of the femoral shaft in children with chronic illness taking glucocorticoids. It does not affect bone growth. Larger controlled studies are needed to determine if these changes translate into reduced fracture incidence or greater peak bone mass. This study highlights the importance of differentiating between changes in bone size and changes in volumetric bone density in assessing bone in children, and also having control subjects in intervention studies.