Metronidazole 400 mg tablets are a prescription medicine commonly used to treat a variety of bacterial and protozoal infections. It works by entering microbial cells and disrupting their DNA structure, which stops the growth and spread of infection. This medication is often prescribed for conditions such as dental infections, bacterial vaginosis, pelvic inflammatory disease, and certain gastrointestinal infections caused by parasites. Metronidazole is usually taken orally and should be used exactly as directed by a healthcare professional to ensure effectiveness and reduce the risk of resistance.