Metronidazole B. Braun (Metronidazole)

• Metronidazole is a nitroimidazole antibiotic used to treat infections caused by anaerobic bacteria and certain protozoa.
• Anaerobic bacterial infections: eliminates susceptible anaerobic organisms, helping resolve intra‑abdominal, skin, and pelvic infections.
• Bacterial vaginosis: reduces Gardnerella vaginalis and associated flora, restoring normal vaginal microbiota.
• Trichomoniasis: eradicates Trichomonas vaginalis, relieving symptoms and preventing transmission.
• Amebic liver abscess: destroys Entamoeba histolytica trophozoites, aiding resolution of hepatic lesions.
• Clostridioides difficile infection: targets toxin‑producing C. difficile, helping control severe colitis.

• Metronidazole is reduced within anaerobic microorganisms to reactive nitro radicals that damage DNA and inhibit nucleic acid synthesis, leading 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 to moderate nausea that may improve with continued dosing.
• Metallic taste: a transient metallic sensation in the mouth during treatment.
• Headache: occasional headache, generally low intensity.
• Diarrhea: mild gastrointestinal upset, usually self‑limiting.
• Dizziness: feeling light‑headed or unsteady, often resolves after therapy.

Serious or Rare Side Effects

• Seizures: rare neurologic events, more likely with high cumulative doses.
• Peripheral neuropathy: tingling, numbness, or burning sensations in hands or feet.
• Severe allergic reactions: rash, swelling, or anaphylaxis requiring immediate medical attention.
• Stevens‑Johnson syndrome: serious skin and mucous membrane disorder with blistering and detachment.

When prescribing Metronidazole, clinicians should consider several safety precautions to minimize risks.

• Pregnancy: Category B – use only if clearly needed after risk‑benefit assessment.
• Alcohol consumption: avoid concurrent alcohol to prevent a disulfiram‑like reaction.
• Renal impairment: dose adjustment may be required; monitor renal function.
• Hepatic impairment: use with caution; monitor liver enzymes during therapy.
• Neurologic effects: discontinue if signs of peripheral neuropathy or seizures develop.
• Store at 2-8°C: keep refrigerated, protect from light, do not freeze.

Metronidazole can interact with several medicines, affecting its efficacy or safety.

Major Interactions (Avoid)

• Alcohol: may cause severe flushing, tachycardia, and hypotension.
• Warfarin: increased anticoagulant effect, raising bleeding risk.
• Lithium: elevated lithium levels, increasing toxicity potential.

Moderate Interactions (Monitor Closely)

• Cimetidine: may raise metronidazole plasma concentrations.
• Oral contraceptives: reduced effectiveness, consider alternative contraception.
• Phenytoin: may lower metronidazole levels, decreasing therapeutic effect.