Used primarily in veterinary medicine and human healthcare as an antibacterial and antiparasitic agent, especially for treating urinary tract infections, respiratory tract infections, meningococcal meningitis, and toxoplasmosis (particularly in immunocompromised patients such as those with HIV). It is effective against a range of Gram-positive and Gram-negative bacteria and certain parasites by inhibiting folic acid synthesis. Commonly combined with other drugs, such as trimethoprim or pyrimethamine, to enhance efficacy through synergistic action. Also used in cell culture media to prevent bacterial contamination. In research, it serves as a model compound in studies of drug resistance and pharmacokinetics. It is a long-acting sulfonamide with good oral absorption and wide distribution throughout the body, including into cerebrospinal fluid.