Overview
Metronidazole is a nitroimidazole antibiotic with antiprotozoal and antibacterial properties, commonly used to treat anaerobic bacterial infections and certain parasitic infections. The topical cream formulation is specifically indicated for inflammatory papules and pustules of rosacea. It works by disrupting DNA synthesis in susceptible microorganisms.
Mechanism of Action
Metronidazole is a nitroimidazole antimicrobial agent that enters bacterial and protozoal cells, where it is reduced to its active form. This active metabolite causes DNA strand breaks and inhibits nucleic acid synthesis, leading to cell death in susceptible anaerobic bacteria and protozoa.
Indications
- Inflammatory papules and pustules of rosacea (topical formulation)
- Anaerobic bacterial infections
- Protozoal infections including trichomoniasis, giardiasis, and amebiasis
- Bacterial vaginosis
- Helicobacter pylori eradication (as part of combination therapy)
- Surgical prophylaxis for colorectal procedures
Common Doses
- Topical cream: 0.75% and 1% strengths
- Oral: 250 mg, 500 mg tablets
- IV: 500 mg/100 mL
Dosage
For topical rosacea treatment: Apply a thin layer twice daily (morning and evening) to affected areas after washing with a mild cleanser. For systemic infections: Typical adult dose is 500-750 mg orally three times daily or 500 mg IV every 6-8 hours, with duration varying by indication.
Contraindications
- Hypersensitivity to metronidazole or other nitroimidazole derivatives
- First trimester of pregnancy for trichomoniasis treatment
- Concurrent use with disulfiram or within 2 weeks of disulfiram therapy
- History of blood dyscrasias with previous metronidazole use
Side Effects
- Common: Nausea, metallic taste, headache, dry mouth
- Gastrointestinal: Anorexia, vomiting, diarrhea, abdominal cramping
- Neurologic: Dizziness, vertigo, peripheral neuropathy
- Dermatologic: Topical application may cause burning, stinging, erythema, or skin irritation
- Hematologic: Reversible neutropenia, thrombocytopenia
- Serious: Seizures, encephalopathy, aseptic meningitis
Interactions
- Alcohol: Disulfiram-like reaction (flushing, nausea, vomiting)
- Warfarin: Potentiates anticoagulant effect, increases INR
- Lithium: May increase lithium levels and toxicity
- Disulfiram: Psychotic reactions
- Phenytoin: May decrease phenytoin metabolism
- Cyclosporine: May increase cyclosporine levels
Counseling Points
- Avoid alcohol consumption during treatment and for at least 48 hours after completion
- Complete full course of therapy even if symptoms improve
- For topical use: Wash area with mild cleanser before application, apply thin layer twice daily
- Report any numbness, tingling, or seizures to healthcare provider immediately
- Use effective contraception during treatment if sexually active