Sulfonamides, also known as sulfa drugs, are a group of synthetic antibiotics that were among the first to be used in medicine. They work by inhibiting the growth of bacteria, specifically by blocking the synthesis of folic acid, which is essential for bacterial reproduction. Sulfonamides are effective against a variety of bacterial infections, including those caused by Streptococcus and Escherichia coli. These medications were widely used in the mid-20th century but have since been largely replaced by more effective antibiotics, such as penicillin. However, sulfonamides are still used today for certain conditions, including urinary tract infections and some types of pneumonia. They are often combined with other drugs to enhance their effectiveness and reduce the risk of resistance.