Nitroimidazole / tetracycline antibiotic combinations are used to treat duodenal ulcers associated with Helicobacter pylori infection. These combinations work by using multiple antibiotics to prevent bacteria from growing normally and making proteins needed to survive, which helps heal ulcers and infections. These medications are usually taken orally. An example is bismuth subcitrate / metronidazole / tetracycline (Pylera).