Metronidazole B. Braun (Metronidazole)

Metronidazole is employed to manage infections caused by anaerobic bacteria and susceptible protozoa.

• Anaerobic bacterial infections: eradicates susceptible anaerobes, reducing infection severity.
• Bacterial vaginosis: restores normal vaginal flora by eliminating pathogenic anaerobes.
• Trichomoniasis: eliminates Trichomonas vaginalis, relieving symptoms.
• Intra‑abdominal infections: controls mixed aerobic‑anaerobic infections following surgery or perforation.
• Pelvic inflammatory disease: treats anaerobic components of PID, improving clinical outcomes.
• Clostridioides difficile‑associated diarrhea (adjunct): reduces toxin‑producing bacterial load when used with standard therapy.

• Metronidazole enters susceptible anaerobic cells and is reduced by microbial ferredoxin proteins, generating nitro radical anions. These reactive intermediates damage DNA, inhibit nucleic acid synthesis, and disrupt critical biomolecules, leading to irreversible bacterial or protozoal cell death while sparing most aerobic host tissues.

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

Common Side Effects

• Nausea: mild to moderate upset stomach.
• Metallic taste: transient metallic sensation in the mouth.
• Headache: occasional dull or throbbing pain.
• Diarrhea: loose stools during therapy.
• Abdominal pain: cramping or discomfort.
• Dizziness: light‑headed feeling.

Serious or Rare Side Effects

• Seizures: rare neurologic events, especially with high doses.
• Severe allergic reactions: anaphylaxis, rash, or angioedema.
• Stevens‑Johnson syndrome: severe skin and mucous membrane involvement.
• Peripheral neuropathy: tingling or numbness in extremities.
• Neutropenia: marked reduction in white blood cells.
• Hepatotoxicity: elevated liver enzymes or liver injury.

Metronidazole requires careful monitoring in specific clinical situations.

• Renal function assessment: adjust use in severe renal impairment.
• Hepatic monitoring: observe liver enzymes during prolonged therapy.
• Pregnancy caution: avoid in the first trimester unless benefits outweigh risks.
• CNS disorders: use cautiously in patients with seizure disorders.
• Allergic reaction: discontinue immediately if severe hypersensitivity occurs.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze or shake.

Metronidazole can interact with several medications, altering efficacy or safety.

Major Interactions (Avoid)

• Alcohol: may cause a disulfiram‑like reaction with flushing and tachycardia.
• Warfarin: potentiates anticoagulant effect, increasing bleeding risk.
• Lithium: may raise lithium levels, leading to toxicity.

Moderate Interactions (Monitor Closely)

• Phenytoin: may reduce metronidazole plasma concentrations.
• Cimetidine: can increase metronidazole levels, enhancing side effects.
• Carbamazepine: may lower metronidazole efficacy, requiring clinical observation.