metronidazole

Metronidazole is an antibiotic and antiprotozoal agent in the nitroimidazole class. It is active against a range of anaerobic bacteria and protozoa and is available in oral tablets, intravenous formulation, and topical preparations for skin and vaginal use.

Mode of action is based on selective uptake and reduction by anaerobic organisms, which produces reactive nitro radical intermediates that damage DNA and other critical macromolecules, leading to cell death. It has little activity against aerobic bacteria.

Common indications include intra‑abdominal and gynecologic infections caused by anaerobes, pelvic inflammatory disease, bacterial vaginosis, trichomoniasis, amoebiasis, giardiasis, and amebic liver abscess. It may be used as part of combination therapy for certain dental and skin infections and as a topical agent for rosacea and other dermatoses.

Pharmacokinetics: metronidazole has high oral bioavailability and distributes widely, including to the central nervous system. It is metabolized in the liver and eliminated mainly in the urine, with an elimination half-life of about 8 hours in adults. Renal impairment may necessitate dose adjustments.

Adverse effects and safety: common adverse effects include nausea, a metallic taste, and headaches. Less commonly, vomiting, dry mouth, dermatitis, and peripheral neuropathy with prolonged use. A disulfiram‑like reaction can occur with alcohol. Rare but serious effects include aseptic meningitis and encephalopathy.

Contraindications and precautions: avoid in hypersensitivity to nitroimidazoles. Use in pregnancy is generally avoided in the first trimester unless clearly needed; later pregnancy use is based on risk–benefit. It is excreted in breast milk; caution is advised during breastfeeding. It can interact with alcohol and with anticoagulants such as warfarin, and may interact with several central nervous system depressants.