Bone Abstracts

Objectives and method: We retrospectively reviewed records of current patients with osteogenesis imperfecta (OI) to identify those on risedronate, doses used and effects of treatment. BMD changes over time were calculated as difference between measurement before risedronate and at one year (including measurements −3–0 m and 10–14 m after starting risedronate respectively).

Results: 219/296 (74%) patients with OI had received bisphosphonates (median 10.92 years; 0.43–19.15). 73/296 (25%) had received risedronate; median starting age 10.21 years (3.76–16.99). 62/73 were started on purely clinical grounds (study patients excluded). 58/62 had mild/moderate OI. Clinical use is increasing (27/62 started in last 2 years).

50/62 were on pamidronate before risedronate; median age starting risedronate 12.35 years (4.1–16.99); mean duration pamidronate 7.1 years (1.14–15.89). Mean pamidronate starting dose was 11.8 mg/kg/year (35/36 on 12 mg/kg/year); reduced to 7.17 mg/kg/year over 12 months before switch to risedronate. 11/61 were bisphosphonate-naive when starting risedronate; most common indication was multiple vertebral fractures (n=8/11).

Mean starting dose of risedronate was 0.95 mg/kg/week (0.34–2.13). Over first 12 m risedronate treatment, mean z-score and % changes in L2–L4 BMD were +0.25 (CI +0.03 to +0.47) and +10.31% (CI 5.88–14.74%), respectively (n=15/61). Mean starting dose was greater in bisphosphonate-naive (1.38 mg/kg/week; 0.97–2.13) than pamidronate-exposed group (0.86 mg/kg/week; 0.34–1.84)(P=0.001). Increase in L2–L4 BMD (z-score; % change) over 12 m after starting risedronate was greater in bisphosphonate-naive (+0.68; 18.99%) than pamidronate-exposed group (+0.10; 7.15%).

Risedronate was discontinued in 14/61; 5/14 stopped for possible adverse effects (4/5 gastrointestinal upset, 1/5 hair loss). 2/14 temporarily discontinued for poor osteotomy healing and following proximal femoral fracture.

Weight-adjusted dose was inversely proportional to age (r²=0.33; P<0.0001). L2–L4 BMD z-score increase over 12 m was directly proportional to dose (intercept 0.8 mg/kg/week; r²=0.44; P=0.01). There is no significant relationship between age and change in z-score (P=0.06) or % change in L2–L4 BMD (P=0.50) over first 12 m of treatment (n=15/61).

Conclusion: Risedronate use has increased in our unit, principally as a substitute for pamidronate in later childhood. Weight-adjusted dose correlated with age, probably due to the preparation available. Doses used and L2–L4 BMD increases are consistent with published studies. We believe there is a place for risedronate in the management of children with OI.

Disclosure: The authors declared no competing interests.