Metronidazole, marketed under the brand name Flagyl among others, is an antibiotic and antiprotozoal medication. It is used either alone or with other antibiotics to treat pelvic inflammatory disease, endocarditis, and bacterial vaginosis. It is effective for dracunculiasis, giardiasis, trichomoniasis, and amebiasis. It is an option for a first episode of mild-to-moderate Clostridium difficile colitis if vancomycin or fidaxomicin is unavailable. Metronidazole is available by mouth, as a cream, and by injection into a vein.
Common side effects include nausea, a metallic taste, loss of appetite, and headaches. Occasionally seizures or allergies to the medication may occur. Some state that metronidazole should not be used in early pregnancy, while others state doses for trichomoniasis are safe. It should not be used when breastfeeding.
Metronidazole began to be commercially used in 1960 in France. It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system. It is available in most areas of the world. The pills are relatively inexpensive, costing between 0.01 and US$0.10 each. In the United States, it is about US$26 for ten days of treatment. In 2016, it was the 71st most prescribed medication in the United States, with more than 11 million prescriptions.