Flagyl 200mg is an antibiotic used to treat various bacterial and parasitic infections. It works by inhibiting the growth of harmful microorganisms, effectively treating conditions like bacterial vaginosis, pelvic inflammatory disease, and certain gastrointestinal infections such as Clostridium difficile. Flagyl is also prescribed for infections caused by parasites, such as giardiasis and amoebiasis. It is typically taken orally in tablet form, and the dosage depends on the severity and type of infection. Common side effects include nausea, headache, and a metallic taste in the mouth.