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# Metrogyl (metronidazole)
## 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.
* **Amebiasis:** Treatment of intestinal amebiasis (amebic dysentery) and amebic liver abscess.
* **Giardiasis:** Treatment of giardiasis.
* **Anaerobic Bacterial Infections:** Treatment of serious anaerobic bacterial infections, including intra-abdominal infections, skin and soft tissue infections, gynecologic infections, bacteremia, bone and joint infections, CNS infections (e.g., brain abscess), and lower respiratory tract infections. Often used in combination with other agents.
* **Pseudomembranous Colitis:** Treatment of *Clostridium difficile*-associated diarrhea.
* **Surgical Prophylaxis:** Prophylaxis against anaerobic infection in contaminated or expectedly contaminated procedures, particularly colorectal surgery.
* **H. pylori Eradication:** Part of multi-drug regimens for *Helicobacter pylori* eradication.
## Adult Dosing
* **Bacterial Vaginosis:** 2 g orally as a single dose, or 500 mg orally twice daily for 7 days.
* **Trichomoniasis:** 2 g orally as a single dose, or 200-250 mg orally three times daily for 7-10 days, or 375 mg orally twice daily for 7 days.
* **Amebiasis:**
* **Intestinal:** 500-750 mg orally three times daily for 5-10 days.
* **Liver Abscess:** 500-750 mg orally three times daily for 5-10 days, followed by a tissue amebicide if the abscess was drained.
* **Giardiasis:** 250 mg orally three times daily for 5-7 days, or 2 g orally once daily for 3 days.
* **Anaerobic Bacterial Infections:**
* **Intravenous (IV):** 15 mg/kg loading dose, followed by 7.5 mg/kg every 6-8 hours for 7-10 days. Maximum daily dose generally 4 g.
* **Oral (PO):** 500 mg every 6-8 hours for 7-10 days. Maximum daily dose generally 4 g.
* **Pseudomembranous Colitis:** 500 mg orally or IV every 8 hours for 10-14 days. (Vancomycin is preferred for severe cases).
* **Surgical Prophylaxis:** 1 g IV as a single dose 1 hour before surgery, or 500 mg orally or IV every 8 hours starting 4 hours before surgery and continuing for up to 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 highly dependent on indication and weight. Consult specific pediatric guidelines.
* **Amebiasis:**
* **Intestinal:** 35-50 mg/kg/day orally divided into 3 doses for 5-10 days. Maximum daily dose 750 mg.
* **Hepatic Abscess:** 35-50 mg/kg/day orally divided into 3 doses for 5-10 days. Maximum daily dose 750 mg.
* **Giardiasis:** 15 mg/kg/day orally divided into 3 doses for 5-7 days. Maximum daily dose 250 mg.
* **Anaerobic Bacterial Infections:**
* **Intravenous (IV):** 7.5 mg/kg every 8 hours.
* **Oral (PO):** 15-35 mg/kg/day divided into 3 doses. Maximum daily dose 4 g.
## Dose Adjustments
* **Renal Impairment:** No dose adjustment generally needed. However, prolonged high doses may require consideration.
* **Hepatic Impairment:** Use with caution in severe hepatic impairment. May require dose reduction or increased dosing interval.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* Use with disulfiram (within 14 days).
* Use with alcohol (during therapy and for at least 3 days after).
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness.
* **Serious:** Peripheral neuropathy (especially with prolonged use), seizures, encephalopathy, aseptic meningitis, Stevens-Johnson syndrome, toxic epidermal necrolysis, pancreatitis, leukopenia, thrombocytopenia, hepatotoxicity.
* **Disulfiram-like reaction:** With alcohol.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, tachycardia). Avoid concurrent use.
* **Warfarin:** Increased anticoagulant effect. Monitor INR closely.
* **Lithium:** May increase lithium levels, leading to toxicity.
* **Phenytoin/Phenobarbital:** May decrease metronidazole levels.
* **Disulfiram:** Potential for psychosis, confusion.
* **Busulfan:** Metronidazole may increase busulfan levels.
* **Cyclosporine:** May increase cyclosporine levels.
## Monitoring
* Monitor for signs and symptoms of peripheral neuropathy (numbness, tingling, pain).
* Monitor for neurological changes (dizziness, confusion, seizures).
* Monitor for signs of hypersensitivity reactions.
* Monitor CBC with differential and platelet count, especially with prolonged or high-dose therapy.
* Monitor INR if co-administered with warfarin.
## Clinical Pearls
* Metronidazole has a bitter, metallic taste that can be reduced by taking with food or by using flavored preparations.
* Urine may turn reddish-brown.
* Advise patients to avoid alcohol during and for at least 3 days after treatment due to the potential for a disulfiram-like reaction.
* For IV administration, reconstitute and dilute according to manufacturer instructions.
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*Disclaimer: This information is intended for healthcare professionals. Always verify current prescribing information with the manufacturer's official product information and relevant clinical guidelines before making any treatment decisions.*
