Metronidazole (MNZ), 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 the drug of choice for a first episode of mild-to-moderate Clostridium difficile colitis. Metronidazole is available by mouth, as a cream, and intravenously.

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 okay. 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 most effective and safe 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 0.10 USD each. In the United States it is about 26 USD for ten days of treatment.