Metronidazole is a nitroimidazole antibiotic and antiprotozoal agent, widely used in the Indian healthcare system. The 600mg strength is a common formulation for systemic infections, particularly for anaerobic and protozoal infections. It is bactericidal and amebicidal, effective against a broad spectrum of anaerobic bacteria and certain parasites.
Adult: Amebiasis: 600-800 mg orally three times daily for 5-10 days. Anaerobic Infections: 400 mg to 600 mg orally every 8 hours. Trichomoniasis/BV: A single 2g dose OR 400-500 mg twice daily for 7 days. H. pylori: 400-500 mg twice or thrice daily as part of combination therapy for 10-14 days.
Note: Take with or after food to minimize gastrointestinal upset. Swallow the tablet whole with a full glass of water. Do not crush or chew. Complete the full prescribed course even if symptoms improve.
Metronidazole is a prodrug. Its nitro group is reduced by low-redox-potential electron transport proteins (ferredoxin or flavodoxin) found in anaerobic bacteria and protozoa. This reduction forms cytotoxic, short-lived nitro radical anions that damage microbial DNA, leading to strand breaks and loss of the helical structure, ultimately causing cell death.
Pregnancy: Pregnancy Category B (US FDA). Avoid in first trimester for trichomoniasis. Use only if clearly needed and benefit outweighs risk. Crosses the placenta.
Driving: May cause dizziness, vertigo, confusion, or visual disturbances. Patients should be cautioned about operating machinery or driving until their response is known.
| Alcohol (Ethanol) | Disulfiram-like reaction: severe nausea, vomiting, flushing, tachycardia, headache. | Major |
| Warfarin | Increased anticoagulant effect, elevated INR, risk of bleeding. | Major |
| Lithium | May increase lithium levels and risk of lithium toxicity. | Moderate |
| Phenytoin, Phenobarbital | May decrease metronidazole levels via enzyme induction. | Moderate |
| Cimetidine | May increase metronidazole levels via CYP450 inhibition. | Moderate |
| 5-Fluorouracil | Increased risk of neurotoxicity. | Moderate |