Sulfonamide antibiotics, also known as sulfa drugs, are a group of synthetic medications used to treat bacterial infections. They work by inhibiting the growth of bacteria by interfering with their ability to produce folic acid, which is essential for their survival. Commonly used sulfonamides include sulfamethoxazole and sulfadiazine. These antibiotics are effective against a variety of infections, including urinary tract infections and certain types of pneumonia. However, they are not effective against viral infections. While sulfonamides were among the first antibiotics discovered, their use has declined due to the development of more effective antibiotics and concerns about resistance and side effects.