Please check your internet connection and try again.
# Metronidazole
## Overview
Metronidazole is a nitroimidazole antibiotic and antiprotozoal agent effective against anaerobic bacteria and certain protozoa.
## Primary Indications
* **Bacterial Vaginosis:** Treatment of bacterial vaginosis.
* **Trichomoniasis:** Treatment of trichomoniasis.
* **Amebiasis:** Treatment of amebiasis (intestinal and extraintestinal).
* **Giardiasis:** Treatment of giardiasis.
* **Anaerobic Bacterial Infections:** Treatment of serious anaerobic bacterial infections (e.g., intra-abdominal infections, skin and soft tissue infections, gynecologic infections, bone and joint infections, CNS infections, lower respiratory tract infections, endocarditis). Often used in combination therapy.
* **_Clostridioides difficile_ Infection:** Treatment of _C. difficile_ infection (CDI), though often reserved for mild-to-moderate disease due to increasing resistance and availability of other agents.
* **Surgical Prophylaxis:** Surgical prophylaxis, particularly in colorectal surgery.
* **Helicobacter pylori Eradication:** Part of multidrug regimens for _H. pylori_ eradication.
## Adult Dosing
Dosing varies significantly by indication.
* **Bacterial Vaginosis:** 500 mg orally twice daily for 7 days, or a single 2 g dose orally. Vaginal gel 0.75% applied once daily for 5 days.
* **Trichomoniasis:** 2 g orally as a single dose, or 250 mg orally three times daily for 7 days, or 375 mg orally twice daily for 7 days.
* **Amebiasis:**
* **Intestinal:** 500-750 mg orally three times daily for 5-10 days.
* **Extra-intestinal (e.g., liver abscess):** 500-750 mg orally or IV three times daily for 5-10 days. Consider luminal agent after completing treatment.
* **Giardiasis:** 250 mg orally three times daily for 5-7 days, or 2 g orally once daily for 3 days.
* **Anaerobic Bacterial Infections:** 500 mg to 1 g IV or orally every 6-8 hours. Duration varies based on severity and site of infection. Max daily dose typically 4 g.
* **_C. difficile_ Infection (CDI):** 500 mg orally three times daily for 10 days (for mild-to-moderate disease).
* **Surgical Prophylaxis:** 1 g IV 1-2 hours before surgery, or 500 mg orally/IV every 8 hours starting 12-24 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 (e.g., proton pump inhibitor and clarithromycin/amoxicillin) for 10-14 days.
## Pediatric Dosing
Dosing is weight-based and depends on the indication.
* **Anaerobic Infections:** 15-35 mg/kg/day orally or IV divided into 3 doses. Maximum daily dose 4 g.
* **Bacterial Vaginosis:** Not typically recommended in pediatric patients unless specifically indicated and guided by specialist.
* **Trichomoniasis:** Not recommended for use in children.
* **Amebiasis:** 35-50 mg/kg/day orally divided into 3 doses for 5-10 days. Maximum daily dose 750 mg.
* **Giardiasis:** 15-25 mg/kg/day orally divided into 3 doses for 5-7 days. Maximum daily dose 250 mg.
* **_C. difficile_ Infection (CDI):** 15 mg/kg/day orally divided into 3 doses for 10 days.
## Dose Adjustments
* **Renal Impairment:** No dose adjustment typically needed for moderate to severe renal impairment. Metronidazole and its metabolites are removed by hemodialysis. Consider supplemental dosing after dialysis.
* **Hepatic Impairment:** No specific dose adjustment is usually recommended. However, use with caution in severe hepatic impairment.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* First trimester of pregnancy (relative contraindication; benefit vs. risk assessment needed).
## 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, thrombophlebitis (with IV administration).
* **Disulfiram-like reaction:** Avoid alcohol during and for at least 3 days after treatment due to potential for severe nausea, vomiting, flushing, and palpitations.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction.
* **Warfarin:** Increased anticoagulant effect. Monitor INR closely and adjust warfarin dose as needed.
* **Lithium:** May increase lithium levels, potentially leading to toxicity. Monitor lithium levels.
* **Phenobarbital and Phenytoin:** May decrease metronidazole levels.
* **Cyclosporine:** May increase cyclosporine levels.
## Monitoring
* Monitor for signs and symptoms of peripheral neuropathy (numbness, tingling, pain).
* Monitor for signs of central nervous system effects (dizziness, confusion, seizures).
* Monitor for gastrointestinal side effects.
* Monitor INR if patient is on warfarin.
* Monitor lithium levels if coadministered.
## Clinical Pearls
* Administer IV metronidazole over 30-60 minutes to minimize risk of thrombophlebitis.
* Advise patients to avoid alcohol during therapy and for at least 3 days after completion.
* A metallic taste is a common side effect and can be managed with good oral hygiene or sugar-free gum.
* For _H. pylori_ eradication, ensure compliance with the full multidrug regimen.
* Metronidazole is often a component of combination therapy for polymicrobial infections, particularly those involving anaerobes.
***
**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and clinical guidelines for complete details. Verify dosages and indications based on specific patient factors and local protocols.
