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# Metrogyl (Metronidazole)
## Overview
Metronidazole is a nitroimidazole antibiotic and antiprotozoal agent. It acts by inducing DNA strand breakage and inhibiting nucleic acid synthesis in susceptible anaerobes and protozoa.
## Primary Indications
* Anaerobic bacterial infections (e.g., intra-abdominal, skin/soft tissue, gynecological).
* *Clostridioides difficile* infection (non-severe).
* Protozoal infections: Trichomoniasis, giardiasis, amebiasis.
* Bacterial vaginosis.
## Adult Dosing
* **Anaerobic Infections:** 500 mg IV/PO every 8 hours. Maximum: 4 g/day.
* **C. difficile infection:** 500 mg PO every 8 hours for 10–14 days.
* **Trichomoniasis:** 2 g PO as a single dose (or 500 mg BID for 7 days).
* **Bacterial Vaginosis:** 500 mg PO BID for 7 days.
## 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: Pediatric dosing varies by indication; always consult weight-based institutional protocols.*
## Dose Adjustments
* **Hepatic Impairment:** Reduce dosage by 50% in patients with severe hepatic impairment (Child-Pugh Class C).
* **Renal Impairment:** Generally no adjustment required for CrCl >10 mL/min. In end-stage renal disease (ESRD), consider a 50% dose reduction due to slower clearance of metabolites.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazoles.
* First trimester of pregnancy (for trichomoniasis treatment).
* Concomitant use of disulfiram within the last 2 weeks.
* Concomitant use of alcohol or propylene glycol-containing products during and for 3 days after therapy (disulfiram-like reaction).
## Adverse Effects
* **Common:** Metallic taste, nausea, headache, dark-colored urine.
* **Serious:** Peripheral neuropathy (with long-term use), seizures, encephalopathy, aseptic meningitis, leukopenia.
## Key Drug Interactions
* **Alcohol:** Severe disulfiram-like reaction (flushing, tachycardia, nausea, vomiting).
* **Warfarin:** Significant potentiation of anticoagulant effect; monitor INR closely.
* **Lithium:** May increase serum levels and risk of toxicity.
* **CYP450 Inducers (e.g., Phenytoin, Phenobarbital):** May decrease metronidazole efficacy.
## Monitoring
* CBC with differential (baseline and periodically during prolonged therapy).
* Neurological status (monitor for tremors, ataxia, or paresthesia).
* INR (if on warfarin).
* Signs of resolution of infection.
## Clinical Pearls
* **Metallic Taste:** Advise patients this is a common side effect and not a sign of allergy.
* **Administration:** May be taken with food to minimize GI upset.
* **Sexual Partners:** In trichomoniasis, both partners must be treated simultaneously to prevent reinfection.
* **IV to PO:** Oral bioavailability is nearly 100%; switch to oral as soon as the patient can tolerate.
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*Disclaimer: This information is for educational purposes and reflects general clinical standards. Dosing and clinical practices may vary by facility, local resistance patterns, and patient-specific factors. Always verify current prescribing information and institutional guidelines before initiating therapy.*
