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# Metrogyl (Metronidazole)
## Overview
Metronidazole is a nitroimidazole antibiotic and antiprotozoal agent. It exhibits bactericidal activity against anaerobic bacteria and protozoa by disrupting DNA synthesis.
## Primary Indications
* Anaerobic bacterial infections (intra-abdominal, skin/soft tissue, gynecological).
* *Clostridioides difficile* infection (second-line or adjunct).
* Protozoal infections: Trichomoniasis, Giardiasis, Amebiasis.
* Bacterial vaginosis.
## Adult Dosing
* **Anaerobic Infections:** 500 mg IV/PO every 8 hours. Max: 4 g/day.
* **Amebiasis:** 500–750 mg PO every 8 hours for 5–10 days.
* **Trichomoniasis:** 2 g PO as a single dose or 500 mg PO twice daily for 7 days.
* **Bacterial Vaginosis:** 500 mg PO twice daily for 7 days.
* **C. difficile:** 500 mg PO/IV every 8 hours for 10–14 days (typically reserved for non-severe cases where vancomycin or fidaxomicin are unavailable).
## Pediatric Dosing
* **Anaerobic Infections:** 30 mg/kg/day divided every 6 hours (Max: 4 g/day).
* **Amebiasis:** 35–50 mg/kg/day divided every 8 hours for 10 days.
* **Giardiasis:** 15 mg/kg/day divided every 8 hours for 5–7 days.
* *Note: Dosing must be adjusted based on the specific indication; consult pediatric pharmacology references or local institutional protocols for neonates.*
## Dose Adjustments
* **Hepatic Impairment:** Reduce dosage by 50% in patients with severe hepatic impairment (Child-Pugh Class C).
* **Renal Impairment:** No standard adjustment for CrCl >10 mL/min. For hemodialysis, consider supplementary dosing post-dialysis depending on the indication.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* First trimester of pregnancy (for trichomoniasis treatment).
* Concurrent use of disulfiram (within last 2 weeks) or alcohol (during and 3 days post-treatment).
## Adverse Effects
* **Common:** Metallic taste, nausea, headache, dizziness, dark-colored urine.
* **Serious:** Peripheral neuropathy (with long-term use), seizures, encephalopathy, optic neuropathy, and rare cases of Stevens-Johnson syndrome. Discontinue immediately if ataxia or paresthesia develops.
## Key Drug Interactions
* **Alcohol:** Triggers a disulfiram-like reaction (flushing, tachycardia, nausea, vomiting).
* **Warfarin:** Significantly potentiates anticoagulant effect; monitor INR closely and adjust warfarin dose as needed.
* **CYP450 Inducers (e.g., Phenytoin, Phenobarbital):** Can decrease metronidazole levels.
* **Lithium:** May increase serum lithium levels and risk of toxicity.
## Monitoring
* **Baseline:** Neurological exam, CBC (if long-term therapy), hepatic function (if severe impairment).
* **During therapy:** Monitor for signs of peripheral neuropathy (numbness/tingling), CNS toxicity, and INR in patients on warfarin.
## Clinical Pearls
* Administer tablets with food to minimize GI upset.
* Advise patients to avoid alcohol for at least 72 hours after the final dose.
* Dark urine is a benign side effect caused by a metabolite; educate patients to prevent unnecessary alarm.
* When treating trichomoniasis, ensure sexual partners are treated concurrently to prevent reinfection.
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*Disclaimer: This information is for educational purposes only. Always verify current prescribing information, institutional guidelines, and drug compatibilities via official labels or clinical decision support tools before prescribing or administering medication.*
