Sivelestat sodium is primarily used as a selective inhibitor of neutrophil elastase, an enzyme that plays a significant role in inflammatory processes. It is commonly applied in the treatment of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), conditions where excessive neutrophil elastase activity contributes to tissue damage and inflammation in the lungs. By inhibiting this enzyme, it helps reduce inflammation and prevent further lung tissue destruction, thereby improving respiratory function. Additionally, it has been explored in research for its potential therapeutic effects in other inflammatory diseases, such as pancreatitis and sepsis, where neutrophil elastase is implicated in disease progression. Its application is particularly critical in intensive care settings for managing severe respiratory complications.