Gramoneg Tablet 8's belongs to a class of drugs called antibiotics used to treat urinary tract infections (UTIs) caused by bacteria. Urinary tract infection is the most common infection in humans caused by microbes and can occur in any part of the urinary tract such as bladder, urethra, kidneys or ureters. Gramoneg Tablet 8's contains Nalidixic acid, an antibiotic that works by inhibiting the action of DNA gyrase (bacterial enzyme) that is essential for repairing and replicating the genetic material (DNA) of bacteria. Thereby prevents reproduction and repair of bacteria. Thus, kills bacteria and clears the infection.