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# Metrogyl (metronidazole)
## Overview
Metronidazole is a nitroimidazole antibiotic and antiprotozoal agent.
## Primary Indications
* **Bacterial Vaginosis:** Treatment of bacterial vaginosis.
* **Trichomoniasis:** Treatment of *Trichomonas vaginalis* infections.
* **Giardiasis:** Treatment of *Giardia lamblia* infections.
* **Amebiasis:** Treatment of *Entamoeba histolytica* infections.
* **Anaerobic Bacterial Infections:** Treatment of serious anaerobic bacterial infections, often in combination with other agents.
## Adult Dosing
* **Bacterial Vaginosis:**
* Vaginal gel 0.75%: Apply 5 g (one applicatorful) vaginally once daily for 5 days.
* Oral: 500 mg twice daily for 7 days.
* **Trichomoniasis:**
* Oral: 2 g as a single dose, OR 250 mg three times daily for 7 days, OR 375 mg twice daily for 7 days.
* **Giardiasis:**
* Oral: 250 mg three times daily for 5 days.
* **Amebiasis:**
* Oral: 500-750 mg three times daily for 7-10 days.
* **Anaerobic Bacterial Infections:**
* Oral: 500 mg every 8 hours.
* IV: 15 mg/kg loading dose, followed by 7.5 mg/kg every 6 hours, or 15 mg/kg every 12 hours. Maximum IV dose typically 4 g/day.
## Pediatric Dosing
Dosing is weight-based and depends on the specific indication and severity. Consult pediatric infectious disease guidelines for precise dosing.
* **Trichomoniasis:** Not recommended for children.
* **Giardiasis:** Oral: 15 mg/kg/day divided into three doses for 5 days. Maximum 250 mg per dose.
* **Amebiasis:** Oral: 35-50 mg/kg/day divided into three doses for 5-10 days. Maximum 750 mg per dose.
* **Anaerobic Bacterial Infections:** Oral/IV: 15-35 mg/kg/day divided into three doses.
## Dose Adjustments
* **Hepatic Impairment:** Use with caution. May require dose reduction.
* **Renal Impairment:** No dose adjustment necessary for routine hemodialysis. For severe renal impairment (CrCl < 10 mL/min) not on dialysis, consideration for reducing the maintenance dose by 50% may be given, though data is limited.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* Use in the first trimester of pregnancy for trichomoniasis (although benefits may outweigh risks in specific situations, consult OB/GYN).
## Adverse Effects
Common: Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness, dark urine.
Serious: Peripheral neuropathy, seizures, Stevens-Johnson syndrome, encephalopathy, leukopenia, thrombophlebitis (IV).
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (severe nausea, vomiting, flushing, headache). Avoid alcohol during and for at least 3 days after metronidazole therapy.
* **Warfarin:** Increased anticoagulant effect. Monitor INR closely.
* **Lithium:** Increased lithium levels, potentially leading to toxicity. Monitor lithium levels.
* **Phenytoin/Phenobarbital:** May decrease metronidazole levels.
## Monitoring
* Monitor for signs and symptoms of peripheral neuropathy (numbness, tingling) and central nervous system effects (seizures, dizziness).
* Monitor stool for resolution of infection.
* Monitor INR if patient is on warfarin.
* Monitor lithium levels if patient is on lithium.
## Clinical Pearls
* Metronidazole can cause a disulfiram-like reaction with alcohol; patients must be counseled to avoid alcohol.
* The metallic taste can be managed by keeping the patient hydrated and using flavoring agents.
* Metronidazole can cause dark or reddish-brown urine; this is benign.
* For vaginal gel, patients should avoid intercourse during treatment.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and professional guidelines before making any treatment decisions.*
