Please check your internet connection and try again.
# Metronidazole (Metrogyl)
## Overview
Metronidazole is a nitroimidazole antibiotic with activity against anaerobic bacteria and protozoa.
## Primary Indications
* **Anaerobic bacterial infections:** Intra-abdominal infections, gynecologic infections, skin and soft tissue infections, bone and joint infections, CNS infections, lower respiratory tract infections, endocarditis.
* **Protozoal infections:** Trichomoniasis, amebiasis, giardiasis.
* **Bacterial vaginosis.**
* **_Clostridioides difficile_ infection** (alternative agent).
* **Prophylaxis** in specific surgical procedures.
* **_Helicobacter pylori_ eradication** (in combination regimens).
## Adult Dosing
Dosing varies significantly based on indication. Common examples include:
* **Anaerobic bacterial infections:** 500 mg IV or PO every 8 hours. Duration 7-10 days or longer depending on infection severity.
* **Bacterial vaginosis:** 500 mg PO BID for 7 days OR 2 g PO single dose OR 0.75% vaginal gel applied once.
* **Trichomoniasis:** 2 g PO single dose OR 250 mg PO TID for 7 days.
* **Amebiasis:**
* Invasive intestinal amebiasis: 500-600 mg PO TID for 7-10 days.
* Amebic liver abscess: 500-600 mg PO TID for 7-10 days.
* **Giardiasis:** 250 mg PO TID for 5-7 days.
* **_H. pylori_ eradication:** Typically 500 mg PO BID in combination with other agents for 10-14 days.
* **Surgical prophylaxis:** 500 mg IV 1 hour prior to incision, followed by 500 mg IV or PO every 8 hours for up to 24 hours postoperatively.
## Pediatric Dosing
Dosing depends on age, weight, and indication. Local protocols are often utilized.
* **Anaerobic bacterial infections:** 7.5 mg/kg/dose IV or PO every 8 hours. Maximum dose: 500 mg per dose or 15 mg/kg/day, whichever is less. Duration varies.
* **Amebiasis:** 35-50 mg/kg/day PO divided into 3 doses for 7-10 days. Maximum 750 mg/day.
* **Giardiasis:** 15 mg/kg/day PO divided into 3 doses for 5-7 days. Maximum 250 mg/dose.
## Dose Adjustments
No dose adjustment is typically needed for renal impairment.
For hepatic impairment, reduce the maintenance dose by 30-50% and administer less frequently (e.g., every 12 hours) due to decreased metabolism.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazoles.
* Use during the first trimester of pregnancy for trichomoniasis (alternative agents preferred).
## Adverse Effects
Common: Nausea, vomiting, diarrhea, metallic taste, headache, dizziness, dark urine.
Less Common: Rash, urticaria, peripheral neuropathy (with prolonged use), seizure, encephalopathy, Stevens-Johnson syndrome.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (severe nausea, vomiting, flushing, headache, tachycardia). Advise patients to avoid alcohol during treatment and for at least 3 days after discontinuation.
* **Warfarin:** Increased anticoagulant effect. Monitor INR closely and adjust warfarin dose as needed.
* **Lithium:** Potential for increased lithium levels, leading to toxicity. Monitor lithium levels.
* **Phenytoin, Phenobarbital:** May decrease metronidazole levels.
* **Cyclosporine:** Potential for increased cyclosporine levels. Monitor cyclosporine levels.
## Monitoring
* Monitor for signs and symptoms of infection resolution.
* Monitor for adverse effects, particularly neurological symptoms and peripheral neuropathy with prolonged use.
* Monitor INR if co-administered with warfarin.
* Monitor lithium levels if co-administered with lithium.
## Clinical Pearls
* Metronidazole has a distinct metallic taste which can affect compliance.
* Administer IV metronidazole over 30-60 minutes to minimize infusion-related reactions.
* Oral metronidazole can be given with or without food; however, taking with food may decrease gastrointestinal upset.
* Ensure adequate hydration when treating _C. difficile_ infections.
***
*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making treatment decisions.*
