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# Metronidazole
## Overview
Metronidazole is an antibiotic and antiprotozoal agent effective against anaerobic bacteria and certain protozoa.
## Primary Indications
* Treatment of anaerobic bacterial infections (e.g., intra-abdominal infections, gynecological infections, skin and soft tissue infections, bone and joint infections, CNS infections, bacterial vaginosis).
* Treatment of protozoal infections (e.g., trichomoniasis, giardiasis, amebiasis).
* Prophylaxis against anaerobic infection in surgical procedures.
## Adult Dosing
* **Anaerobic bacterial infections:** 500 mg IV or PO every 8 hours for 7-10 days. Higher doses may be required for specific infections.
* **Bacterial vaginosis:** 500 mg PO BID for 7 days, or 2 g PO as a single dose.
* **Trichomoniasis:** 2 g PO as a single dose, or 250 mg PO TID for 7 days.
* **Giardiasis:** 250 mg PO TID for 5-7 days, or 2 g PO once daily for 3 days.
* **Amebiasis:**
* **Intestinal amebiasis:** 500-750 mg PO TID for 5-10 days.
* **Amebic liver abscess:** 500-750 mg PO TID for 5-10 days, followed by a luminal agent.
* **Surgical prophylaxis:** 1 g PO or IV 1-2 hours before surgery, followed by 500 mg PO or IV every 8 hours for up to 24 hours post-operatively.
## Pediatric Dosing
Dosing in pediatric patients varies significantly based on indication and weight. Consult specific pediatric guidelines. Generally:
* **Anaerobic bacterial infections:** 15 mg/kg/day IV or PO divided every 8 hours, not to exceed 4 g/day.
* **Bacterial vaginosis:** Not typically recommended.
* **Trichomoniasis:** Not typically recommended.
* **Giardiasis:** 5 mg/kg/dose PO TID for 5-7 days, not to exceed 250 mg/dose.
* **Amebiasis:** 35-50 mg/kg/day PO divided TID for 5-10 days, not to exceed 750 mg/dose.
## Dose Adjustments
* **Hepatic Impairment:** Use with caution. Reduce dose by 50% in severe hepatic disease.
* **Renal Impairment:** No dose adjustment is generally needed for intermittent hemodialysis. For continuous renal replacement therapy (CRRT), specific recommendations vary; consult local protocols.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* Use within 14 days of disulfiram therapy.
* Active central nervous system (CNS) disease.
## Adverse Effects
Common: Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness.
Serious: Peripheral neuropathy (especially with prolonged use), seizures, Stevens-Johnson syndrome, encephalopathy, optic neuropathy, leukopenia, pancreatitis.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, headache, palpitations). Advise patients to avoid alcohol during and for at least 3 days after therapy.
* **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.
* **Phenytoin, Phenobarbital:** May decrease metronidazole levels.
* **Cyclosporine:** May increase cyclosporine levels. Monitor cyclosporine levels.
## Monitoring
* Monitor for signs and symptoms of infection.
* Monitor for adverse effects, particularly neuropathy (numbness, tingling, pain).
* Monitor INR if co-administered with warfarin.
* Monitor lithium levels if co-administered with lithium.
## Clinical Pearls
* Metronidazole has a metallic taste, which can affect patient compliance.
* Advise patients to complete the full course of therapy even if symptoms improve.
* Metronidazole can turn urine a dark or reddish-brown color.
* Neurological side effects, including peripheral neuropathy, have been reported, particularly with prolonged or high-dose therapy.
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*This information is intended for healthcare professionals and does not substitute for professional medical advice. Always consult the most current prescribing information and guidelines before administering any medication.*
