Sefdin 300 mg Capsule belongs to a class of medication called 'antibiotics' used to treat several bacterial infections of the urinary tract, bones and joints, heart, lungs, brain, chest, ears, skin or soft tissues. Bacterial infection is when harmful bacteria grow in the body and cause infection. It can infect any part of the body and multiply very quickly. Sefdin 300 mg Capsule does not work against infections caused by a virus such as flu or a common cold.