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# Metronidazole (Metrogyl)
## Overview
Metronidazole is an antimicrobial agent effective against anaerobic bacteria and certain protozoa.
## Primary Indications
* **Bacterial vaginosis:** Treatment of bacterial vaginosis.
* **Trichomoniasis:** Treatment of symptomatic trichomoniasis.
* **Giardiasis:** Treatment of giardiasis.
* **Amebiasis:** Treatment of amebiasis (intestinal and extraintestinal).
* **Anaerobic bacterial infections:** Treatment of serious anaerobic bacterial infections, often in combination with other agents. Examples include intra-abdominal infections, gynecologic infections, skin and soft tissue infections, bone and joint infections, CNS infections, lower respiratory tract infections, and endocarditis.
* **Pseudomembranous colitis:** Treatment of Clostridioides difficile-associated diarrhea.
* **Surgical prophylaxis:** Preoperative prophylaxis in certain surgical procedures (e.g., colorectal surgery).
## Adult Dosing
* **Bacterial Vaginosis:**
* Oral: 500 mg orally twice daily for 7 days, OR 2 grams orally as a single dose.
* Vaginal gel: 0.75% gel, 5 grams (one applicatorful) inserted vaginally once daily for 5 days.
* **Trichomoniasis:**
* Oral: 2 grams orally as a single dose, OR 250 mg orally three times daily for 7 days, OR 375 mg orally twice daily for 7 days.
* **Giardiasis:**
* Oral: 250 mg orally three times daily for 5 to 7 days.
* **Amebiasis:**
* Oral: 500-750 mg orally three times daily for 5 to 10 days.
* IV: 500 mg to 1 g every 8 hours.
* **Anaerobic bacterial infections:**
* Oral/IV: 500 mg every 8 hours. Duration varies by infection site and severity (often 7-14 days). Higher doses may be used for severe infections (e.g., 1 g IV every 8 hours).
* **Pseudomembranous colitis:**
* Oral: 500 mg every 8 hours. Duration is typically 10-14 days.
* **Surgical prophylaxis:**
* Oral/IV: 500 mg given just prior to surgery. Oral doses may be repeated for extended procedures.
## Pediatric Dosing
Dosing in pediatric patients can vary based on indication, weight, and infection severity. Specific protocols should be consulted.
* **Amebiasis:**
* Oral: 35-50 mg/kg/day divided into 3 doses for 5-10 days.
* **Giardiasis:**
* Oral: 15 mg/kg/day divided into 3 doses for 5-7 days. Maximum 750 mg/day.
* **Bacterial infections (anaerobic):**
* IV: 30 mg/kg/day divided into 3 doses. Can be increased to 40 mg/kg/day for severe infections, not to exceed adult maximum.
## Dose Adjustments
* **Renal Impairment:** No dose adjustment is typically needed. Metronidazole and its metabolites are removed by hemodialysis.
* **Hepatic Impairment:** Use with caution. Reduce dose in severe hepatic disease.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* Active central nervous system disease.
* History of blood dyscrasias.
## Adverse Effects
Common adverse effects include:
* Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain, metallic taste.
* Neurologic: Dizziness, headache, peripheral neuropathy (especially with prolonged use).
* Other: Darkened urine, rash, pruritus, candidiasis.
Less common but serious: seizures, encephal
