Please check your internet connection and try again.
# Metronidazole
## Overview
Metronidazole is a synthetic nitroimidazole antibiotic with activity against anaerobic bacteria and certain protozoa.
## Primary Indications
* **Bacterial Vaginosis:** Treatment of bacterial vaginosis.
* **Trichomoniasis:** Treatment of trichomoniasis.
* **Amoebiasis:** Intestinal and extraintestinal amoebiasis.
* **Giardiasis:** Treatment of giardiasis.
* **Anaerobic Bacterial Infections:** Treatment of serious anaerobic bacterial infections (e.g., intra-abdominal infections, skin and soft tissue infections, gynecological infections, bone and joint infections, CNS infections, lower respiratory tract infections, endocarditis). Often used in combination therapy.
* **Pseudomembranous Colitis:** Treatment of *Clostridioides difficile*-associated diarrhea (CDAD).
* **Surgical Prophylaxis:** Prophylaxis against anaerobic infection in specific surgical procedures (e.g., colorectal surgery).
* **H. pylori Eradication:** Part of multi-drug regimens for *Helicobacter pylori* eradication.
## Adult Dosing
* **Bacterial Vaginosis:** 500 mg orally twice daily for 7 days, or a single dose of 2 grams orally.
* **Trichomoniasis:** 2 grams orally as a single dose, or 500 mg orally twice daily for 7 days.
* **Amoebiasis:**
* Intestinal: 500-675 mg orally 3 times daily for 5-10 days.
* Extra-intestinal (e.g., liver abscess): 500-675 mg orally 3 times daily for 5-10 days. A luminal amoebicide may be required after treatment.
* **Giardiasis:** 250 mg orally 3 times daily for 5-7 days.
* **Anaerobic Bacterial Infections:** 500 mg IV or orally every 8 hours. Duration varies based on severity and site of infection. For severe infections, doses up to 1 gram IV every 8 hours may be used.
* **Pseudomembranous Colitis (CDAD):** 500 mg orally every 8 hours. Metronidazole is generally considered second-line to vancomycin for severe CDAD.
* **Surgical Prophylaxis:** 1 gram orally or IV 1-2 hours before surgery, or 500 mg orally or IV every 8 hours starting prior to surgery and continuing for up to 24 hours postoperatively.
* ***H. pylori* Eradication:** Dosing varies by regimen; commonly 500 mg orally twice daily or 3 times daily in combination with other agents.
## Pediatric Dosing
Dosing in children is typically based on weight and indication. Consult specific pediatric guidelines.
* **Giardiasis:** 15 mg/kg/day orally divided into 3 doses, not to exceed 250 mg per dose, for 5-7 days.
* **Anaerobic Bacterial Infections:** 7.5 mg/kg IV or orally every 8 hours. For severe infections, doses up to 15 mg/kg IV or orally every 8 hours may be used, not to exceed 4 grams/day.
## Dose Adjustments
* **Hepatic Impairment:** Use with caution and consider dose reduction, especially in severe hepatic impairment.
* **Renal Impairment:** No dose adjustment is generally required for the parent drug. However, consider potential accumulation of metabolites in severe renal impairment (CrCl < 10 mL/min).
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazoles.
* Concomitant use with disulfiram or alcohol due to disulfiram-like reaction.
* First trimester of pregnancy (though often used if benefits outweigh risks).
## Adverse Effects
Common: Nausea, vomiting, diarrhea, abdominal discomfort, metallic taste, headache, dizziness.
Less Common: Rash, urticaria, pruritus, dark or red-brown urine, peripheral neuropathy (especially with prolonged use), seizures, encephalopathy, Stevens-Johnson syndrome, toxic epidermal necrolysis.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, tachycardia, dyspnea). Avoid alcohol during and for at least 3 days after metronidazole therapy.
* **Disulfiram:** Potential for acute psychosis and confusional states.
* **Warfarin:** Increased INR and risk of bleeding. Monitor INR closely and adjust warfarin dose as needed.
* **Lithium:** Potential for lithium toxicity. Monitor lithium levels.
* **Phenobarbital:** Decreased efficacy of metronidazole.
* **Phenytoin:** Decreased efficacy of metronidazole.
* **Cyclosporine:** Potential for increased cyclosporine levels. Monitor cyclosporine levels.
* **5-Fluorouracil (5-FU):** Potentially increased toxicity of 5-FU.
## Monitoring
* Monitor for signs and symptoms of CDAD if applicable.
* Monitor for peripheral neuropathy, especially with prolonged treatment courses.
* Monitor INR if co-administered with warfarin.
* Monitor lithium levels if co-administered with lithium.
## Clinical Pearls
* Metallic taste is common and can be managed with good oral hygiene.
* Avoid alcohol during and for 3 days after treatment.
* IV metronidazole is a good agent for anaerobic coverage in serious infections.
* The disulfiram-like reaction is significant and requires patient education.
* Consider the potential for neuropathy with prolonged therapy.
***
This information is intended for healthcare professionals and does not replace a thorough review of the most current prescribing information and clinical guidelines. Always verify current drug information before making clinical decisions.
