Introduction: In Duchenne muscular dystrophy and in the mdx mouse, muscle fiber degeneration and subsequent fibrosis lead to cardiorespiratory failure. Previously, we demonstrated that the anti-fibrotic agent suramin was effective in decreasing fibrosis in mdx muscles. In this study, we were interested to see whether suramin could affect metalloproteinases (MMP) and improve the functional activity of the mdx diaphragm muscle. Methods: Zymography was performed to evaluate MMP-2 and MMP-9 activity. Western blotting was used to analyze the levels of beta-dystroglycan. Muscle function was assessed in hemidiaphragm in vitro preparations. Results: We found that suramin affects metalloproteinase-9 activity and increases beta-dystroglycan. Furthermore, suramin also protects against diaphragm muscle fatigue over time. 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