Please check your internet connection and try again.
# Metronidazole
## Overview
Metronidazole is an antimicrobial agent effective against anaerobic bacteria and certain protozoa.
## Primary Indications
* Bacterial vaginosis
* Trichomoniasis
* Amebiasis
* Giardiasis
* Anaerobic bacterial infections (e.g., intra-abdominal infections, C. difficile infection, pelvic inflammatory disease, bacterial vaginosis)
* Surgical prophylaxis (colorectal surgery)
## Adult Dosing
* **Bacterial Vaginosis:** 500 mg orally twice daily for 7 days, or a single 2-gram dose orally.
* **Trichomoniasis:** 2-gram single oral dose, or 250 mg orally twice daily for 7 days.
* **Amebiasis:**
* Invasive intestinal amebiasis: 500-600 mg orally three times daily for 7-10 days.
* Amebic liver abscess: 500-600 mg orally three times daily for 7-10 days.
* **Giardiasis:** 250 mg orally three times daily for 5-7 days, or 500 mg orally twice daily for 3 days.
* **Anaerobic bacterial infections:** 500 mg orally or IV every 8 hours. Duration varies based on infection severity and site, typically 7-14 days.
* **C. difficile infection:**
* Mild-to-moderate: 500 mg orally three times daily for 10-14 days.
* Severe: Vancomycin is generally preferred.
* **Surgical Prophylaxis (colorectal):** 1 gram IV 1-2 hours before surgery, or 500 mg orally every 8 hours starting 24 hours before surgery and continued for 24 hours post-op.
## Pediatric Dosing
Dosing varies significantly by indication and weight. Consult specific pediatric infectious disease guidelines or pediatric formularies for precise dosing.
* **Giardiasis:** 15 mg/kg/day orally divided into 3 doses, not to exceed 250 mg per dose, for 5-7 days.
* **Amebiasis:** 35-50 mg/kg/day orally divided into 3 doses, not to exceed 750 mg per dose, for 7-10 days.
## Dose Adjustments
Renal impairment: No dose adjustment is typically needed for mild to moderate renal impairment. In severe renal impairment, consider reducing the dose, especially with prolonged therapy, though data is limited.
Hepatic impairment: Reduce dose by 50% in severe hepatic impairment.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* First trimester of pregnancy (relative contraindication for trichomoniasis; safety in later pregnancy and for other indications should be evaluated).
* Use within 14 days of disulfiram or alcohol consumption.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, metallic taste, anorexia, headache, dizziness.
* **Serious:** Peripheral neuropathy (especially with prolonged use), seizures, encephalopathy, aseptic meningitis, Stevens-Johnson syndrome, pancreatitis, leukopenia, thrombophlebitis (IV).
* **Disulfiram-like reaction:** Severe nausea, vomiting, flushing, tachycardia, and shortness of breath with concomitant alcohol use.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction. Avoid alcohol during and for at least 3 days after therapy.
* **Warfarin:** Potentiates anticoagulant effect. Monitor INR closely and adjust warfarin dose as needed.
* **Lithium:** May increase lithium levels, potentially leading to toxicity. Monitor lithium levels.
* **Phenytoin/Phenobarbital:** May decrease metronidazole levels and efficacy.
* **Disulfiram:** Increased risk of psychiatric symptoms.
## Monitoring
* Monitor for signs and symptoms of peripheral neuropathy (numbness, tingling, pain) and central nervous system effects (dizziness, confusion, seizures).
* Monitor INR if used concomitantly with warfarin.
* Monitor lithium levels if used concomitantly with lithium.
* Monitor for diarrhea, especially if prolonged, to rule out C. difficile recurrence or development.
## Clinical Pearls
* The metallic taste is a common and often bothersome side effect.
* Advise patients to avoid alcohol during and for 3 days after treatment.
* IV formulation should be administered as a slow infusion.
* For trichomoniasis, sexual partners should also be treated.
***
*This information is intended for healthcare professionals and does not replace a thorough review of the current prescribing information or clinical guidelines. Always verify the most up-to-date information with official drug labeling and institutional protocols.*
