metronidazole UKMetronidazole 400 mg is an antibiotic used to treat a range of bacterial and parasitic infections, including dental infections, bacterial vaginosis, pelvic inflammatory disease, and certain gastrointestinal infections such as those caused by anaerobic bacteria. In the UK, metronidazole is a prescription-only medicine, meaning it cannot be legally purchased over the counter and must be prescribed by a qualified healthcare professional after an assessment of your condition. It works by stopping the growth of microorganisms, helping the body’s immune system clear the infection. It is important to take the full prescribed course even if symptoms improve early. Common side effects may include nausea, a metallic taste, and stomach discomfort. Alcohol should be avoided during treatment and for at least 48 hours after finishing, as it can cause unpleasant reactions.