Metronidazole B. Braun Melsungen (Metronidazole)

Metronidazole is a nitroimidazole antibiotic used to treat infections caused by anaerobic bacteria and certain protozoa.

• Anaerobic bacterial infections: effective in eradicating mixed anaerobic infections in intra‑abdominal, pelvic, and skin‑soft tissue sites.
• Bacterial vaginosis: restores normal vaginal flora by eliminating Gardnerella and other anaerobes.
• Trichomoniasis: eliminates Trichomonas vaginalis infection in women.
• Amebic liver abscess: treats Entamoeba histolytica hepatic infection.
• Clostridioides difficile infection: used as part of therapy for severe C. difficile colitis.

• Metronidazole is taken up by anaerobic microorganisms and reduced by ferredoxin‑type proteins to generate nitro radical anions. These reactive metabolites bind to DNA, causing strand breakage and inhibiting nucleic acid synthesis, which leads to bacterial and protozoal cell death while sparing aerobic cells.

Metronidazole may cause a range of adverse reactions, varying from mild to severe.

Common Side Effects

• Nausea: mild gastrointestinal upset.
• Metallic taste: transient dysgeusia.
• Headache: mild to moderate intensity.
• Diarrhea: loose stools.
• Abdominal pain: crampy discomfort.
• Rash: mild skin erythema.

Serious or Rare Side Effects

• Seizures: neurologic events.
• Peripheral neuropathy: tingling or numbness.
• Stevens‑Johnson syndrome: severe skin reaction.
• Hepatotoxicity: elevated liver enzymes.
• Anaphylaxis: acute allergic response.
• Methemoglobinemia: reduced oxygen carrying capacity.

Before using Metronidazole, consider the following precautions to ensure safe and effective therapy.

• Renal impairment: adjust dosing in severe renal dysfunction.
• Hepatic disease: monitor liver function tests.
• Alcohol consumption: avoid alcohol due to disulfiram‑like reaction.
• Pregnancy: use only if clearly needed; risk unknown.
• Lactation: discontinue nursing or stop drug as it may be excreted in milk.
• Concomitant neurotoxic drugs: monitor for additive neuropathy.
• Store at ambient temperature: keep below 25°C, protect from moisture and light in original container.

Metronidazole can interact with several medicines, altering efficacy or increasing toxicity.

Major Interactions (Avoid)

• Alcohol: causes severe flushing, tachycardia, and nausea.
• Warfarin: may enhance anticoagulant effect, increasing bleeding risk.
• Lithium: can raise lithium levels, leading to toxicity.

Moderate Interactions (Monitor Closely)

• Phenytoin: may reduce metronidazole levels.
• Cimetidine: may increase metronidazole plasma concentration.
• Carbamazepine: may decrease metronidazole effectiveness.
• Phenobarbital: may lower metronidazole concentrations.