Please check your internet connection and try again.
# Metronidazole (Metrogyl)
## Overview
Metronidazole is an antibiotic and antiprotozoal agent.
## Primary Indications
* Treatment of anaerobic bacterial infections (e.g., intra-abdominal infections, skin and soft tissue infections, gynecological infections, bacterial vaginosis).
* Treatment of protozoal infections (e.g., trichomoniasis, giardiasis, amebiasis).
* *Helicobacter pylori* eradication.
* Surgical prophylaxis.
## Adult Dosing
* **Anaerobic Infections:** Typically 500 mg IV or PO every 8 hours. Duration varies based on infection severity and site, often 7-14 days. Maximum dose generally 4 g/day.
* **Bacterial Vaginosis:** 500 mg PO BID for 7 days, or 2 g PO single dose.
* **Trichomoniasis:** 2 g PO single dose, or 500 mg PO BID for 7 days.
* **Giardiasis:** 250 mg PO TID for 5-7 days, or 2 g PO once daily for 3 days.
* **Amebiasis:**
* *Intestinal:* 500-650 mg PO TID for 7-10 days.
* *Hepatic Abscess:* 500-650 mg PO TID for 7-10 days.
* ***H. pylori* Eradication:** Varies in combination regimens, commonly 500 mg PO BID or TID for 10-14 days.
* **Surgical Prophylaxis:** 1 g IV 1-2 hours before surgery, then 500 mg IV or PO every 8 hours for up to 12 hours postoperatively.
## Pediatric Dosing
Dosing varies significantly by indication and weight. Consult specific pediatric guidelines or resources.
* **Anaerobic Infections:** Typically 7.5 mg/kg/dose IV or PO every 8 hours. Maximum single dose 15 mg/kg, maximum daily dose 4 g.
* **Giardiasis:** 5 mg/kg/dose PO TID for 5-7 days.
* **Amebiasis:** 35-50 mg/kg/day PO divided into 3 doses for 7-10 days.
## Dose Adjustments
No dose adjustment is typically needed in mild to moderate renal impairment. In severe renal impairment or with peritoneal dialysis/hemodialysis, dose reduction (e.g., to one-third or one-half the usual dose) may be considered, or dosing interval increased, due to potential accumulation. Dose adjustment is not required in hepatic impairment unless severe.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* First trimester of pregnancy (relative contraindication, used only if clearly needed).
* Concurrent use of disulfiram or alcohol due to potential disulfiram-like reaction.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness.
* **Serious:** Peripheral neuropathy (especially with prolonged use), seizures, encephalopathy, Stevens-Johnson syndrome, pancreatitis, leukopenia, thrombocytosis.
* **Disulfiram-like Reaction:** Severe nausea, vomiting, flushing, palpitations, and headache if alcohol is consumed during and up to 3 days after treatment.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction. Avoid alcohol during and for at least 3 days after treatment.
* **Warfarin:** May potentiate anticoagulant effect. Monitor INR closely and adjust warfarin dose as needed.
* **Lithium:** May increase lithium levels, potentially leading to toxicity. Monitor lithium levels.
* **Disulfiram:** Concurrent use is contraindicated.
* **Phenytoin, Phenobarbital:** May decrease metronidazole levels.
* **5-Fluorouracil:** May increase toxicity of 5-FU.
## Monitoring
* Monitor for signs and symptoms of infection resolution.
* Monitor for adverse effects, particularly neuropathy (numbness, tingling, pain) and mental status changes.
* Monitor INR if patient is on warfarin.
* Monitor lithium levels if patient is on lithium.
* Monitor CBC if prolonged treatment or in patients with a history of blood dyscrasias.
## Clinical Pearls
* Metronidazole has activity against anaerobic bacteria and protozoa.
* The metallic taste is common and can be mitigated by using flavored agents or chilling the medication.
* Concurrent alcohol use can cause a severe disulfiram-like reaction; patients must be counseled to avoid alcohol.
* Neuropathy can be irreversible; patients should be advised to report any sensory disturbances.
* For *H. pylori* eradication, compliance is critical for success.
This information is intended for healthcare professionals. Always consult the current prescribing information and relevant clinical guidelines for complete details and to ensure patient-specific appropriateness.
