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# Metronidazole
## Overview
Metronidazole is a nitroimidazole antibiotic effective against anaerobic bacteria and certain protozoa.
## Primary Indications
* Bacterial vaginosis
* *Clostridioides difficile* infection (CDI)
* Intra-abdominal infections
* Gynecologic infections
* Skin and soft tissue infections
* Surgical prophylaxis
* Trichomoniasis
* Giardiasis
* Amebiasis
## Adult Dosing
Dosing varies significantly by indication and severity. Common regimens include:
* **Bacterial Vaginosis:** 500 mg orally twice daily for 7 days, or a single 2 g dose orally.
* ***Clostridioides difficile* Infection (CDI):** 500 mg orally three times daily for 10-14 days. (Note: Vancomycin is often preferred for severe or initial episodes).
* **Trichomoniasis:** 2 g orally as a single dose.
* **Giardiasis:** 250 mg orally three times daily for 5-7 days.
* **Amebiasis (intestinal):** 500-750 mg orally three times daily for 5-10 days.
* **Intra-abdominal Infections (adjunct):** 500 mg IV every 8 hours, often in combination with other agents.
Maximum daily oral dose is generally 4 g.
## Pediatric Dosing
Dosing varies by indication and weight.
* **Bacterial infections:** 7.5 to 15 mg/kg/dose orally or IV every 8 hours. Maximum dose 4 g/day.
* **Trichomoniasis/Giardiasis/Amebiasis:** 5-12 mg/kg/dose orally every 8 hours.
## Dose Adjustments
No specific dose adjustment is typically needed for hepatic or renal impairment unless severe. In severe hepatic impairment, consider reducing the dose by 30-50%.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazoles.
* Concomitant use of disulfiram or alcohol (disulfiram-like reaction).
## Adverse Effects
* Nausea, vomiting, metallic taste
* Diarrhea
* Headache, dizziness
* Darkened urine
* Peripheral neuropathy (with prolonged use)
* Seizures (rare)
* Pancreatitis (rare)
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, tachycardia). Advise avoidance during therapy and for at least 72 hours after.
* **Warfarin:** Increased anticoagulant effect. Monitor INR closely.
* **Lithium:** Potential for increased lithium levels. Monitor lithium levels.
* **Phenytoin, Phenobarbital:** May decrease metronidazole levels.
* **Disulfiram:** Concurrent use is contraindicated due to potential for psychotic reactions.
## Monitoring
* Monitor for signs and symptoms of C. difficile recurrence.
* Monitor for peripheral neuropathy with prolonged therapy.
* Monitor lithium and INR levels if co-administered with lithium or warfarin, respectively.
## Clinical Pearls
* Administer oral metronidazole with food to minimize gastrointestinal upset.
* IV metronidazole can be infused undiluted or diluted in compatible IV fluids.
* Avoid alcoholic beverages during and for at least 72 hours after treatment.
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*This information is intended for clinical use and does not replace professional judgment. Always verify current prescribing information with the manufacturer's official product information or other reliable resources before making clinical decisions.*
