Gramocef-O 400 mg Tablet DT is an antibiotic belonging to the cephalosporin group which is used to treat a variety of bacterial infections. It is effective in infections of the respiratory tract (eg. pneumonia) urinary tract ear nasal sinus throat and some sexually transmitted diseases. Gramocef-O 400 mg Tablet DT is an antibiotic that belongs to a group of medicine called cephalosporins. It works by stopping the growth of infection-causing bacteria in your body. It is effective for bacterial infections of the lungs throat and urinary tract among others. This medicine usually makes you feel better within a few days but you should continue taking it as prescribed even when you feel better. Stopping it early may make the infection come back and harder to treat.