In Duchenne Muscular Dystrophy (DMD) there is an imbalance between the levels of calcium and sodium in the muscles cells which is thought to be important in the damage which occurs overtime. Sodium/proton type 1 exchanger (NHE-1) inhibition is an innovative pathway that has proved to efficiently prevent the accumulation of muscle damage (inflammation and fibrosis) in animal models of muscular dystrophies and heart failure. Based on prior safety and efficacy results in animal and humans, NHE-1 inhibition with Rimeporide represents a new therapeutic approach with no restriction on age and on genetic subtypes which could be combined to other treatments that restore or augment dystrophin.This study examines the safety and tolerability and effects on the muscles of rimeporide, in patients aged 6 to 14 years with Duchenne Muscular Dystrophy (DMD).