Cefasyn 500 Tablet is an antibiotic prescribed to treat bacterial infections in the body. Cefasyn 500 Tablet is a versatile antibiotic that eliminates infection-causing bacteria in the body. This drug is used to treat a wide range of infections, including those of the lungs (pneumonia), ear, abdomen, urinary tract, bones, joints, skin, and soft tissues. This medication normally relieves your symptoms within a few days, but you should continue to take it as directed even if you feel better. Stopping it early may cause the infection to resurface and become more difficult to cure.