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# Metronidazole
## Overview
Metronidazole is an antimicrobial agent effective against anaerobic bacteria and certain protozoa.
## Primary Indications
* **Bacterial Vaginosis:** Treatment of bacterial vaginosis.
* **Trichomoniasis:** Treatment of symptomatic trichomoniasis.
* **Amoebiasis:** Treatment of intestinal and extraintestinal amoebiasis.
* **Giardiasis:** Treatment of giardiasis.
* **Anaerobic Bacterial Infections:** Treatment of serious anaerobic bacterial infections, often in combination with other agents.
## Adult Dosing
* **Bacterial Vaginosis:** 500 mg orally twice daily for 7 days, OR 2 grams orally as a single dose.
* **Trichomoniasis:** 2 grams orally as a single dose, OR 250 mg orally three times daily for 7 days, OR 500 mg orally twice daily for 7 days.
* **Amoebiasis:**
* Intestinal: 500-650 mg orally three times daily for 5-10 days.
* Extra-intestinal (e.g., liver abscess): 500-650 mg orally three times daily for 5-10 days, followed by a luminal agent.
* **Giardiasis:** 250 mg orally three times daily for 5 days, OR 500 mg orally twice daily for 7 days.
* **Anaerobic Bacterial Infections:** 500 mg intravenously or orally every 8 hours. Duration varies based on infection severity and site, typically 7-14 days.
## Pediatric Dosing
Dosing is typically weight-based and depends on the indication. Consult specific pediatric guidelines for precise dosing.
* **Amoebiasis:** 35-50 mg/kg/day orally in 3 divided doses for 5-10 days. Maximum dose typically 750 mg per dose.
* **Giardiasis:** 15 mg/kg/day orally in 3 divided doses for 5 days. Maximum dose typically 250 mg per dose.
* **Serious Anaerobic Infections:** 30 mg/kg/day intravenously or orally in 3-4 divided doses. Maximum dose typically 4 grams/day.
## Dose Adjustments
* **Hepatic Impairment:** Use with caution. Dosing may need to be reduced, especially in severe hepatic insufficiency. Some sources suggest reducing the maintenance dose by 50% in severe hepatic disease.
* **Renal Impairment:** No specific dose adjustment is generally recommended for intermittent hemodialysis or peritoneal dialysis. However, for severe renal impairment (CrCl < 10 mL/min), consider reducing the maintenance dose by 50% if the drug is not removed by dialysis.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* First trimester of pregnancy (risk-benefit assessment required for other trimesters).
* Use within 14 days of disulfiram or alcohol consumption.
## Adverse Effects
Common: Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness.
Serious: Peripheral neuropathy (especially with prolonged use), seizures, encephalopathy, Stevens-Johnson syndrome, leukopenia, thrombophlebitis (IV).
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (severe nausea, vomiting, flushing, palpitations). Avoid alcohol during treatment and for at least 3 days after discontinuation.
* **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 efficacy.
* **Cyclosporine:** Metronidazole may increase cyclosporine levels. Monitor cyclosporine levels.
* **Disulfiram:** Concomitant use is contraindicated due to potential for psychotic reactions.
## Monitoring
* Monitor for signs and symptoms of peripheral neuropathy (numbness, tingling, pain).
* Monitor for neurological adverse effects (dizziness, confusion, seizures).
* Monitor CBC if treatment is prolonged or in patients with a history of blood dyscrasias.
* Monitor INR if co-administered with warfarin.
* Monitor lithium levels if co-administered with lithium.
## Clinical Pearls
* The metallic taste is common and can be reduced by taking with food.
* Urine may become reddish-brown due to metabolites; this is usually harmless.
* Discontinue if peripheral neuropathy or central nervous system symptoms develop.
* Metronidazole is effective against specific anaerobic bacteria and protozoa; it is not effective against aerobic bacteria.
This information is intended as a concise summary. Always consult the most current prescribing information and institutional protocols for complete details and to ensure patient-specific appropriateness.
**Disclaimer:** This drug information is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment. Review the official prescribing information for the most up-to-date and complete details.
