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# Metronidazole (Metrogyl)
## Overview
Metronidazole is an antibiotic and antiprotozoal agent.
## Primary Indications
* Treatment of anaerobic bacterial infections (e.g., intra-abdominal infections, gynecologic infections, skin and soft tissue infections, bone and joint infections, CNS infections, bacteremia).
* Treatment of *Clostridioides difficile* infection (CDI).
* Treatment of protozoal infections (e.g., trichomoniasis, amebiasis, giardiasis).
* Surgical prophylaxis (e.g., colorectal surgery).
* Part of multi-drug regimens for *Helicobacter pylori* eradication.
## Adult Dosing
Dosing varies significantly by indication.
* **Anaerobic infections:** Typically 500 mg intravenously or orally every 8 hours. Duration depends on severity and site of infection, often 7-14 days.
* ***C. difficile* infection:** 500 mg orally every 8 hours for 10-14 days for initial episode or recurrence.
* **Trichomoniasis:** 2 g orally as a single dose, or 200 mg orally three times daily for 7 days.
* **Amebiasis:**
* **Intestinal:** 500-650 mg orally every 8 hours for 7-10 days.
* **Extra-intestinal (hepatic abscess):** 500-650 mg orally every 8 hours for 7-10 days, followed by a luminal agent.
* **Giardiasis:** 250 mg orally three times daily for 5-7 days.
* **Surgical prophylaxis (colorectal):** 1 g orally or intravenously as a single dose 1 hour before surgery, or 500 mg every 8 hours starting before surgery and continuing for 24 hours postoperatively.
* ***H. pylori* eradication:** Typically 500 mg orally twice daily in combination with other agents for 10-14 days.
## Pediatric Dosing
Dosing is weight-based and varies by indication. Consult specific pediatric guidelines.
* **Anaerobic infections:** Typically 7.5 mg/kg/dose intravenously or orally every 8 hours. Maximum dose is generally 500 mg per dose.
* ***C. difficile* infection:** 7.5 mg/kg/dose orally every 8 hours for 10-14 days. Maximum dose is generally 500 mg per dose.
## Dose Adjustments
No specific dose adjustment is required for hepatic impairment, but caution is advised due to potential accumulation. In severe hepatic impairment, the maintenance dose may need to be reduced. No dose adjustment is needed for renal impairment.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* Disulfiram-like reaction with alcohol.
## Adverse Effects
Common adverse effects include nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, and dizziness.
Serious adverse effects include:
* Peripheral neuropathy (especially with prolonged use).
* Seizures.
* Encephalopathy.
* Aseptic meningitis.
* Stevens-Johnson syndrome/toxic epidermal necrolysis.
* Pancreatitis.
* Leukopenia.
* Hepatotoxicity.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, headache). Avoid concurrent use.
* **Warfarin:** Increased anticoagulant effect. Monitor INR closely.
* **Lithium:** Increased lithium levels, potential for toxicity. Monitor lithium levels.
* **Phenytoin/Phenobarbital:** May decrease metronidazole efficacy.
* **Oral Contraceptives:** May decrease efficacy.
* **Cyclosporine:** Increased cyclosporine levels. Monitor cyclosporine levels.
## Monitoring
* Monitor for signs and symptoms of neuropathy (numbness, tingling, pain) and CNS effects (dizziness, confusion, seizures).
* Monitor CBC if prolonged therapy or high doses are used.
* Monitor INR if used concurrently with warfarin.
* Monitor lithium levels if used concurrently with lithium.
## Clinical Pearls
* Administer oral metronidazole with food to minimize gastrointestinal upset.
* Intravenous metronidazole is typically infused over 20-60 minutes.
* A metallic taste is common and usually resolves after discontinuation.
* Concurrent use of alcohol should be strictly avoided during therapy and for at least 72 hours after the last dose.
* For trichomoniasis, treat sexual partners concurrently.
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***Disclaimer:** This information is intended for clinical pharmacists and healthcare professionals. It is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions. Dosing and indications may vary based on specific patient factors and local protocols.*
