Résumé :
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Background : Corticosteroids are effective in delaying the loss of muscle strength leading to prolongation of ambulation in patients with Duchenne muscular dystrophy (DMD). The recommended dose for prednisone in ambulatory boys is daily 075 mg/kg/day but is limited by high incidence of adverse effects. Objectives : The primary objective was to compare the difference in change in mean Manual Muscle Testing (MMT) scores in ambulatory boys with DMD aged 5-10 years on intermittent prednisolone (0.75 mg/kg/day 10 days a month) with those on daily prednisolone (0.75 mg/kg/day) at 6 months of therapy. The secondary objectives were to compare timed functions (Gower time, 9 m walking time, Four stair climb time), peak torque and average power ( isokinetic muscle testing by dynamometry) and Forced Vital Capacity (FVC) in the two groups. Methods : Randomized, single blind (outcome assessor), open label parallel group trial conducted at AIIMS, New Delhi, India. Boys with DMD diagnosed on the basis of genetic testing and/or muscle biopsy were randomized to either Daily or Intermittent group. Results : Seventy two patients were randomly assigned to receive either daily (36) or intermittent (36) prednisolone therapy. 11/ 72 patients (15%) did not follow study plan and were lost to follow up. The difference in change in mean MMT score between two groups after 6 months of therapy was less than the hypothesized value of 0.2 (Mean change was 0.19±0.15, 95 % CI 0.14 to 0.25 in daily group versus 0.10±0.11, 95 % CI- 0.06-0.18 in intermittent group).Thus, the intermittent regime was non-inferior to daily prednisolone in improving muscle strength in ambulatory DMD boys. However, the mean improvement in Gower time and four stair climb time was significantly more in daily group as compared to intermittent group. On isokinetic testing, the change in mean peak torque was not significant in the two groups. However, the improvement in average power in daily group(0.5±0.32 W, 95%CI 0.37-0.63) was significantly more than in intermittent group (0.29±0.34W, 95%CI 0.15-0.42, p=0.002). The change in mean FVC (litres and percent predicted) was not significantly different among the two groups.Conclusion: Intermittent prednisolone therapy is probably non-inferior to daily prednisolone in improving muscle strength as assessed by change in mean MMT scores after 6 months of therapy. However the improvement in functional abilities and average power (isokinetic testing) was significantly better with daily therapy. Thus larger multicentric prospective studies should be carried out with loss of ambulation, timed functions or quantitative muscle testing as primary outcome.
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