Metronidazole (Flagyl)

• Generic name: Metronidazole
• Brand/Trade names: Flagyl
• Dosages:
  Tablets 250 mg, 500 mg; Capsules 375 mg; Cream 0.75%; Gel 0.75%;
• Pharmacologic category: Antiprotozoal, antibacterial agent
• FDA approved: July 18, 1963
• Habit forming? No
• Pregnancy risk factor: B

Metronidazole is classified as a nitroimidazole antiprotozoal and antibacterial agent. Metronidazole is used to treat protozoal infections and anaerobic bacterial infections.

• Amebiasis
• Symptomatic and asymptomatic trichomoniasis
• Skin and skin structure infections
• CNS infections
• Intra-abdominal infections (as part of combination regimen)
• Antibiotic-associated pseudomembranous colitis (AAPC)
• Bacterial vaginosis

The most common side effects are gastrointestinal, particularly nausea reported by about 12% of patients, sometimes accompanied by headache, anorexia, and occasionally vomiting; diarrhea; epigastric distress; and abdominal cramping. Constipation has also been reported.

• Elimination half-life: 8 h in healthy adults, and the hydroxy-metabolite half-life is 15 h.
• Metabolism: Metabolized presumably in the liver
• Excretion: Main route of elimination is by kidney but it is also secreted in bile and breast milk. 77% is recovered from urine and 14% from stool.

• Low cost.

• Alcohol interaction. Drinking alcohol while taking metronidazole can cause severe nausea, vomiting, flushing and rapid heart rate. A disulfiram-like reaction may occur if alcohol is ingested within 7 days of use.
• Possible carcinogenic potential. Metronidazole is carcinogenic to animals. It has shown to have tumorigenic activity in mice and rats, the most prominent being pulmonary lesions in the mouse. Unnecessary use of the drug should be avoided.

• Antibiotic-associated colitis. Oral metronidazole for 10 to 14 days may be helpful as first-line therapy for antibiotic-associated colitis.
• Crohn's disease. Studies3 have shown that metronidazole can be effective in keeping symptoms of Crohn's disease from coming back after surgery. Other studies2 have shown that metronidazole relieved symptoms of Crohn's disease, especially in the colon.
  Metronidazole may be used to treat infections that develop because of Crohn's disease, especially when abscesses, abnormal connections (fistulas) between two parts of the intestines; treat active disease and may help with symptoms when aminosalicylates do not; keep symptoms of Crohn's disease from coming back after surgery.
• Hepatic encephalopathy. Hepatic encephalopathy is brain and nervous system damage that occurs as a complication of liver disorders. Hepatic encephalopathy is an acute medical condition that may become a medical emergency. Metronidazole4 is used to reduce colonic flora in the treatment of hepatic encephalopathy, and
  has shown to be as effective as neomycin.
• Giardiasis. Giardiasis is a major diarrheal disease found throughout the world. Metronidazole5 is usually is taken in tablet form for 3 to 7 days for treatment of giardiasis.
• Helicobacter Pylori. Helicobacter Pylori is capable of surviving in the harsh acidic environment of the stomach. The bacteria can directly damage the stomach's protective mucous lining, decrease the body's ability to defend itself and cause an increase in acid production leading to the development of an ulcer, or sore. Some of the treatment regimens use metronidazole6.

Metronidazole is an antiprotozoal and anaerobic antibacterial agent. Metronidazole works by inhibiting bacterial DNA synthesis hence preventing the replication of bacteria.

However the mechanisms by which topical metronidazole works in reducing inflammatory lesions of rosacea are unknown. Possible mechanisms of action include antibacterial and/or anti-inflammatory effects.

• Flagyl community ratings on RevolutionHealth.com
• Flagyl (Metronidazole) reviews, ratings by patients on DrugLib.com
• Metronidazole user reviews for bacterial vaginitis, bacterial infection on Drugs.com
• Flagyl user reviews about treatment success rate on DailyStrength.org

• 1. U.S. Food and Drug Administration. Metronidazole (Flagyl) U.S. Prescribing Information. Available at (PDF format): Prescribing Information
• 2. Prantera C, Berto E, Scribano ML, Falasco G. Use of antibiotics in the treatment of active Crohn's disease: experience with metronidazole and ciprofloxacin. Ital J Gastroenterol Hepatol. 1998 Dec;30(6):602-6. PubMed
• 3. Froehlich F, Juillerat P, Felley C, Mottet C, Vader JP, Burnand B, Michetti P, Gonvers JJ. Treatment of postoperative Crohn's disease. Digestion. 2005;71(1):49-53.
• 4. Morgan MH, Read AE, Speller DC. Treatment of hepatic encephalopathy with metronidazole. Gut. 1982 Jan;23(1):1-7
• 5. Alizadeh A, Ranjbar M, Kashani KM, Taheri MM, Bodaghi M. Albendazole versus metronidazole in the treatment of patients with giardiasis in the Islamic Republic of Iran. East Mediterr Health J. 2006 Sep;12(5):548-54. PubMed
• 6. Matsuhisa T, Kawai T, Masaoka T, Suzuki H, Ito M, Kawamura Y, Tokunaga K, Suzuki M, Mine T, Takahashi S, Sakaki N. Efficacy of metronidazole as second-line drug for the treatment of Helicobacter pylori Infection in the Japanese population: a multicenter study in the Tokyo Metropolitan Area. Helicobacter. 2006 Jun;11(3):152-8. PubMed

Last modified: April, 2010