Metronidazole

Metronidazole, sold under the brand name Flagyl and Metrogyl 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 Clostridioides difficile colitis if vancomycin or fidaxomicin is unavailable. Metronidazole is available orally (by mouth), as a cream or gel, and by slow intravenous infusion (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.

Metronidazole began to be commercially used in 1960 in France. It is on the World Health Organization's List of Essential Medicines. It is available in most areas of the world. In 2023, it was the 203rd most commonly prescribed medication in the United States, with more than 2 million prescriptions.

Metronidazole has activity against some protozoans and most anaerobic bacteria (both Gram-negative and Gram-positive classes) but not the aerobic bacteria.

Metronidazole is primarily used to treat: bacterial vaginosis, pelvic inflammatory disease (along with other antibacterials like ceftriaxone), pseudomembranous colitis, aspiration pneumonia, rosacea (topical), fungating wounds (topical), intra-abdominal infections, lung abscess, periodontal disease, amoebiasis, oral infections, giardiasis, trichomoniasis, and infections caused by susceptible anaerobic organisms such as Bacteroides, Fusobacterium, Clostridium, Peptostreptococcus, and Prevotella species. It is also often used along with other drugs to eradicate Helicobacter pylori and to prevent infection in people recovering from surgery.

Metronidazole is bitter and so the liquid suspension contains metronidazole benzoate. This may require hydrolysis in the gastrointestinal tract and some sources speculate that it may be unsuitable in people with diarrhea or feeding-tubes in the duodenum or jejunum.

Drugs of choice for the treatment of bacterial vaginosis include metronidazole and clindamycin.

An effective treatment option for mixed infectious vaginitis is a combination of clotrimazole and metronidazole.