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# Metronidazole (Metrogyl)
## Overview
Metronidazole is an antibiotic and antiprotozoal agent effective against anaerobic bacteria and certain parasites.
## Primary Indications
* **Bacterial Vaginosis:** Treatment of vaginal infections caused by bacteria.
* **Trichomoniasis:** Treatment of parasitic infections.
* **Amebiasis:** Treatment of parasitic infections of the intestine and liver.
* **Giardiasis:** Treatment of parasitic infections of the intestine.
* **Anaerobic bacterial infections:** Treatment of various infections caused by susceptible anaerobic organisms (e.g., intra-abdominal infections, skin and soft tissue infections, gynecological infections, bone and joint infections, CNS infections, lower respiratory tract infections, endocarditis, septicemia).
* **Bacterial Vaginosis (BV):** Treatment of BV.
## Adult Dosing
* **Bacterial Vaginosis:**
* Oral: 500 mg twice daily for 7 days, or 2 grams as a single dose.
* Vaginal Gel 0.75%: 5 grams (one applicatorful) intravaginally once daily for 5 days.
* **Trichomoniasis:**
* Oral: 2 grams as a single dose, or 250 mg twice daily for 7 days, or 375 mg twice daily for 7 days.
* **Amebiasis:**
* Invasive intestinal amebiasis: 500-675 mg three times daily for 5-10 days.
* Hepatic amebic abscess: 500-675 mg three times daily for 5-10 days.
* **Giardiasis:**
* Oral: 250 mg three times daily for 5-7 days.
* **Anaerobic bacterial infections:**
* Oral/IV: 500 mg every 8 hours. Duration varies by infection site and severity, typically 7-10 days.
* Surgical prophylaxis (colorectal surgery): IV: 1 gram within 12 hours before surgery, then 500 mg every 8 hours for up to 24 hours.
## Pediatric Dosing
Dosing in children depends on the indication, weight, and severity of infection. Consult specific pediatric guidelines or drug references for precise dosing. Generally, oral doses range from 15-50 mg/kg/day divided into 2-3 doses for various infections.
## Dose Adjustments
* **Hepatic Impairment:** Use with caution. Reduce dosage in severe hepatic disease.
* **Renal Impairment:** No dose adjustment is generally required for hemodialysis patients; however, consult specific guidelines as the drug may be removed by dialysis. For other degrees of renal impairment, dose adjustment is typically not necessary.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* Concurrent use of disulfiram or alcohol.
## Adverse Effects
Common: Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness, rash.
Serious: Peripheral neuropathy (especially with prolonged use), seizures, encephalopathy, Stevens-Johnson syndrome, candidiasis, pancreatitis.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, tachycardia). Avoid alcohol during therapy and for at least 3 days after.
* **Warfarin:** Increased anticoagulant effect. Monitor INR closely.
* **Lithium:** May increase lithium levels, potentially leading to toxicity.
* **Disulfiram:** Concomitant use is contraindicated due to potential for psychotic reactions.
* **Phenytoin, Phenobarbital:** May decrease metronidazole levels.
## Monitoring
* Monitor for signs and symptoms of neuropathy (numbness, tingling, pain).
* Monitor for gastrointestinal upset.
* Monitor for signs of superinfection (e.g., oral or vaginal candidiasis).
* For BV, assess clinical improvement.
## Clinical Pearls
* Metronidazole has a metallic taste that can be bothersome.
* It is effective against *Trichomonas vaginalis*, *Entamoeba histolytica*, and *Giardia lamblia*.
* The drug concentrates in cerebrospinal fluid and breast milk.
* Urine may become reddish-brown in color.
* Patient counseling regarding alcohol avoidance is crucial.
Please verify current prescribing information for the most up-to-date dosing, indications, and safety information.
