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# Metronidazole
## Overview
Metronidazole is a nitroimidazole antibiotic and antiprotozoal agent.
## Primary Indications
* Treatment of anaerobic bacterial infections (e.g., intra-abdominal infections, skin and soft tissue infections, gynecologic infections, bone and joint infections, CNS infections).
* Treatment of protozoal infections (e.g., trichomoniasis, amebiasis, giardiasis).
* Treatment of *Clostridioides difficile* infection (CDI).
* Surgical prophylaxis.
## Adult Dosing
* **Anaerobic Infections:** Typically 500 mg IV every 8 hours, or 15 mg/kg IV once followed by 7.5 mg/kg IV every 8 hours. Duration varies by infection site and severity. Oral doses are often 250-500 mg PO every 8 hours.
* **Trichomoniasis:** 2 g PO single dose, or 250 mg PO BID for 7 days, or 375 mg PO BID for 7 days.
* **Amebiasis:**
* *Invasive Intestinal Amebiasis:* 500-750 mg PO TID for 5-10 days.
* *Amebic Liver Abscess:* 500-750 mg PO TID for 5-10 days, followed by a luminal agent.
* ***C. difficile* Infection (CDI):** 500 mg PO TID for 10-14 days. IV formulation may be used if oral administration is not possible.
* **Surgical Prophylaxis:** 1 g IV 1-2 hours before surgery, or 500 mg PO every 8 hours for 24 hours.
## Pediatric Dosing
Dosing varies significantly by indication and patient weight. Consult specific pediatric guidelines.
* **Anaerobic Infections:** Typically 7.5 mg/kg IV or PO every 8 hours. Maximum dose usually 4 g/day.
* ***C. difficile* Infection:** 10-15 mg/kg/day PO divided every 8 hours for 10-14 days. Maximum dose usually 4 g/day.
* **Amebiasis:** 35-50 mg/kg/day PO divided every 8 hours for 5-10 days. Maximum dose usually 750 mg/day.
* **Trichomoniasis:** Not generally recommended in children <12 years.
## Dose Adjustments
* **Renal Impairment:** No dose adjustment generally needed for moderate to severe renal impairment. Hemodialysis can significantly reduce metronidazole levels; a supplemental dose may be required after dialysis.
* **Hepatic Impairment:** Use with caution. May require dose reduction in severe hepatic impairment.
## Contraindications
* Known hypersensitivity to metronidazole or other nitroimidazoles.
* First trimester of pregnancy (relative contraindication, especially for non-emergent indications).
* Concurrent use with disulfiram or alcohol (due to disulfiram-like reaction).
## Adverse Effects
Common: Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness.
Serious: Peripheral neuropathy (especially with prolonged use), seizures, encephalopathy, Stevens-Johnson syndrome, pancreatitis, neutropenia.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, tachycardia, palpitations). Avoid alcohol during therapy and for at least 3 days after.
* **Warfarin:** Increased anticoagulant effect. Monitor INR closely.
* **Lithium:** Increased lithium levels, potentially leading to toxicity.
* **Phenytoin/Phenobarbital:** May decrease metronidazole efficacy.
* **Disulfiram:** Co-administration is contraindicated.
## Monitoring
* Monitor for signs and symptoms of peripheral neuropathy (numbness, tingling, pain).
* Monitor for signs of CNS toxicity (dizziness, confusion, seizures).
* Monitor for signs of *C. difficile* recurrence or treatment failure.
* Monitor INR if co-administered with warfarin.
## Clinical Pearls
* A metallic taste is a common side effect but usually resolves after treatment.
* Concurrent use with alcohol should be strictly avoided.
* Oral suspension is often preferred for pediatric patients requiring liquid formulations.
* For trichomoniasis, sexual partners should also be treated.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult current prescribing information and relevant guidelines before making any treatment decisions.
