Metronidazole B. Braun (Metronidazole)

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

• Intra‑abdominal and pelvic infections: helps eradicate anaerobic bacteria, reducing infection severity.
• Bacterial vaginosis: restores normal vaginal flora by eliminating pathogenic anaerobes.
• Trichomoniasis: eliminates Trichomonas vaginalis, relieving symptoms.
• Clostridioides difficile‑associated colitis: suppresses toxin‑producing C. difficile strains.
• Amebic liver abscess: destroys Entamoeba histolytica organisms, aiding resolution of hepatic lesions.

• Metronidazole is reduced in anaerobic microorganisms to generate nitro‑radical metabolites that interact with DNA, causing strand breakage and loss of helical structure. This damage inhibits nucleic acid synthesis and leads to cell death in susceptible bacteria and protozoa, while aerobic cells are largely spared.

Metronidazole may cause a range of adverse reactions.

Common Side Effects

• Nausea: mild stomach upset may occur.
• Metallic taste: transient metallic sensation in the mouth.
• Headache: occasional mild headache.
• Diarrhea: loose stools may develop.

Serious or Rare Side Effects

• Seizures: rare neurologic events.
• Peripheral neuropathy: tingling or numbness in extremities.
• Severe allergic reaction: rash, swelling, or anaphylaxis.
• Hepatotoxicity: elevated liver enzymes or liver injury.

Use Metronidazole with attention to patient‑specific factors and monitoring.

• Renal impairment: dose may need adjustment and renal function should be monitored.
• Hepatic dysfunction: monitor liver enzymes; use with caution in severe liver disease.
• Alcohol consumption: avoid, as a disulfiram‑like reaction can occur.
• Pregnancy: category B; prescribe only when benefit outweighs potential risk.
• Concurrent warfarin therapy: monitor INR closely due to possible potentiation of anticoagulant effect.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Metronidazole interacts with several medicines; some require avoidance while others need careful monitoring.

Major Interactions (Avoid)

• Alcohol: may cause severe nausea, vomiting, and flushing (disulfiram‑like reaction).
• Lithium: increased lithium levels can lead to toxicity.
• Warfarin: potentiates anticoagulant effect; INR monitoring is essential.

Moderate Interactions (Monitor Closely)

• Cimetidine: may raise metronidazole plasma concentrations.
• Phenobarbital: can reduce metronidazole levels, decreasing efficacy.
• Phenytoin: may lower metronidazole effectiveness through enzyme induction.