Metronidazole

Nursing pharmacology study reference (NCLEX-style monograph). Numeric values are standard teaching ranges for study and must be verified against current manufacturer labeling before clinical use. This is educational content, not prescribing guidance.

Metronidazole (brand name Flagyl) — Antibacterial, antiprotozoal; Nitroimidazole.

Identification

• Therapeutic class: Antibacterial, antiprotozoal.
• Pharmacologic class: Nitroimidazole.

Pharmacology

• Mechanism of action: Damages microbial DNA in anaerobes and protozoa (bactericidal).
• Onset / peak / duration: Rapid; usually three times daily PO.
• Half-life / therapeutic level: Half-life about 8 hours; no routine level.

Clinical use

• Indications: Anaerobic infections, C. difficile (alternative), bacterial vaginosis, trichomoniasis, giardiasis, H. pylori regimens.
• Usual dose, route, frequency: PO three times daily; IV; topical and vaginal forms.
• Maximum dose / adjustments: Reduce in severe hepatic impairment.

Safety

• Contraindications: First trimester of pregnancy (for some uses), alcohol use, hypersensitivity.
• Black box warning: None (animal carcinogenicity caution on label).
• Interactions: Alcohol (disulfiram-like reaction with flushing, vomiting; avoid alcohol during and for 3 days after, food/drink), warfarin (raises INR), lithium, disulfiram (psychosis).
• Pregnancy / lactation: Avoid first trimester for nonurgent use.
• High-alert: No.

Adverse effects

• Common side effects: Metallic taste, nausea, dark urine, headache.
• Serious effects to report: Peripheral neuropathy, seizures, severe disulfiram-like reaction.
• Antidote / reversal: Supportive care.

Nursing process

• Assessment before administration: Alcohol use, neuro baseline, pregnancy status.
• Interventions during therapy: Reinforce strict alcohol avoidance; monitor for neuropathy with long courses.
• Monitor: Neuro status, INR if on warfarin, infection resolution.
• Evaluation / expected outcome: Resolution of infection.

Patient teaching

• Patient teaching: Absolutely no alcohol during and for 3 days after; harmless dark urine; report numbness.
• Notify provider if: Numbness or tingling, severe flushing or vomiting after alcohol, seizures.
• Administration tips: With food for GI upset; avoid all alcohol.