Metronidazole is bactericidal and is used primarily against anaerobes and certain protozoans.

Pharmacology

Oral metronidazole is absorbed well. IV use is generally needed only for patients who cannot be treated orally. It is distributed widely in body fluids and penetrates into CSF in high concentrations. Metronidazole is metabolized presumably in the liver and excreted mainly in urine, but elimination is not decreased in patients with renal insufficiency. Doses are usually decreased 50% in patients with significant liver disease.

Indications

Metronidazole is active against all obligate anaerobic bacteria and certain protozoan parasites (eg, Trichomonas vaginalis , Entamoeba histolytica , Giardia lamblia).

Metronidazole is used primarily for infections caused by obligate anaerobes (eg, intra-abdominal, pelvic, soft-tissue, periodontal, and odontogenic infections, and lung abscess), often with other antimicrobials. Metronidazole is the drug of choice for bacterial vaginosis. It has been used in Crohn's disease. It is effective in meningitis, brain abscess, endocarditis, and septicemia. Metronidazole has also been used for prophylaxis after intestinal surgery. It is effective for Clostridium difficile colitis when given orally or, in patients unable to take oral medication, IV. Metronidazole, in combination with other drugs, is effective for peptic ulcers due to Helicobacter pylori and prevents relapses. Metronidazole has been used topically and orally to treat acne rosacea.

Toxicity

Nausea, vomiting, headache, seizures, syncope, other CNS reactions, and peripheral neuropathy can occur; rash, fever, and reversible neutropenia have been reported. It can cause a metallic taste and dark urine. A disulfiram-like reaction may occur if alcohol is ingested within 7 days of use. Metronidazole inhibits metabolism of warfarin and may increase its anticoagulant effect. Although metronidazole is in the FDA category B (meaning the drug is unlikely to be harmful to the fetus), metronidazole should be avoided during the 1st trimester of pregnancy because of concerns about its mutagenicity.

Last full review/revision November 2005