Metronidazole antibiotic is marketed by Pfizer under the trade name Flagyl, and also by various generic manufacturers, who sell it at a cheaper price. Antibiotics will not work for colds, flu, or other viral infections. Metronidazole is a valuable antibiotic and is generally well tolerated with appropriate use. Metronidazole is an antibiotic effective against anaerobic bacteria and certain parasites. Metronidazole is usually taken two or three times a day for ten days or longer. It at a cheaper price. Flagyl possesses a wide spectrum of action in the attitude to anaerobic microorganisms.