Risedronate in the treatment of mild pediatric osteogenesis imperfecta: a randomized placebo-controlled study

Intravenous pamidronate is the most widely used treatment for moderate to severe osteogenesis imperfecta (OI). Currently, there is no medical treatment for patients with mild OI. We conducted a single-center randomized double-blind placebo-controlled trial to examine the efficacy and safety of oral risedronate in the treatment of pediatric patients with mild OI. A total of 26 children and adolescents (age, 6.1-17.7 yr; 11 girls) with OI type I were randomized to either placebo (N = 13) or risedronate (N = 13) for 2 yr. Risedronate doses were 15 mg once per week in patients weighing <40 kg and 30 mg once per week in patients weighing >40 kg. After 2 yr of treatment, risedronate decreased serum levels of the bone resorption marker collagen type I N-telopeptide by 35% compared with a 6% reduction with placebo (p = 0.003). Risedronate increased lumbar spine areal BMD Z-scores by 0.65, whereas patients receiving placebo experienced a decrease of 0.15 (p = 0.002). In contrast, no significant treatment differences in bone mass and density were found at the radial metaphysis and diaphysis, the hip, and the total body. Histomorphometric analysis of transiliac bone biopsies at the end of the study period did not show a significant treatment difference in cortical width, trabecular bone volume, or parameters of bone turnover. Similarly, there was no detectable treatment effect on vertebral morphometry, second metacarpal cortical width, grip force, bone pain, or number of new fractures. Regarding safety, risedronate was generally well tolerated, and the incidence of clinical or laboratory adverse experiences was similar among treatment groups. These results suggest that the skeletal effects of oral risedronate are weaker than those that are commonly observed with intravenous pamidronate treatment but still lead to an increase in lumbar spine areal BMD. Future studies should investigate whether oral risedronate is effective in reducing fracture rates in children and adolescents with mild OI type I.