Iclaprim mesylate is primarily used as an antibacterial agent, particularly in the treatment of acute bacterial skin and skin structure infections (ABSSSI). It works by inhibiting bacterial dihydrofolate reductase, an enzyme crucial for bacterial DNA synthesis, thereby stopping the growth of susceptible bacteria. This makes it effective against Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA). It is often considered as an alternative for patients who cannot tolerate other antibiotics or when resistance to other treatments is a concern. Its targeted mechanism of action and efficacy against resistant strains make it a valuable option in combating challenging bacterial infections.