Metronidazole 400 mg tablets are an antibiotic and antiprotozoal medicine commonly used to treat a variety of bacterial and parasitic infections. It is often prescribed for conditions such as dental infections, bacterial vaginosis, pelvic inflammatory disease, stomach infections caused by certain parasites, and infections of the stomach, skin, joints, and respiratory tract. The medicine works by stopping the growth of bacteria and parasites, helping the body clear the infection effectively. Metronidazole should be taken exactly as prescribed by a healthcare professional, usually with food to reduce stomach upset. It is important to complete the full course even if symptoms improve early. Common side effects may include nausea, headache, or a metallic taste.