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# Metrogyl (metronidazole)
## Overview
Metronidazole is an antibiotic and antiprotozoal agent effective against anaerobic bacteria and certain parasites.
## Primary Indications
* Bacterial Vaginosis
* Trichomoniasis
* Amebiasis
* Giardiasis
* Anaerobic bacterial infections (e.g., intra-abdominal infections, skin and soft tissue infections, gynecologic infections, bone and joint infections, CNS infections, lower respiratory tract infections, endocarditis, C. difficile infection)
* Surgical prophylaxis
## Adult Dosing
* **Bacterial Vaginosis:** 500 mg orally twice daily for 7 days OR 2 g orally once daily for 1 day.
* **Trichomoniasis:** 2 g orally once daily for 1 day OR 250 mg orally twice daily for 7 days OR 375 mg orally twice daily for 7 days.
* **Amebiasis:** 500-750 mg orally every 8 hours for 5-10 days.
* **Giardiasis:** 250 mg orally three times daily for 5-7 days OR 500 mg orally twice daily for 5 days.
* **Anaerobic Bacterial Infections:** 500 mg IV or orally every 8 hours. Duration varies based on infection site and severity. Max dose generally 4 g/day.
* **C. difficile Infection:** 500 mg orally every 8 hours for 10-14 days.
* **Surgical Prophylaxis:** 1 g orally or IV 1-2 hours before surgery, then 500 mg orally or IV every 8 hours for up to 24 hours post-operatively.
## Pediatric Dosing
Dosing is weight-based and depends on the indication. Consult specific pediatric guidelines or infectious disease specialists for precise dosing.
* **General Anaerobic Infections:** 15 mg/kg/day orally or IV divided into 3 doses, not to exceed 4 g/day. Maintenance dose: 7.5 mg/kg/dose every 8 hours.
* **Giardiasis:** 5 mg/kg/dose orally three times daily for 5 days, not to exceed 250 mg/dose.
* **Amebiasis:** 35-50 mg/kg/day orally or IV divided into 3 doses for 5-10 days, not to exceed 750 mg/dose.
## Dose Adjustments
* **Hepatic Impairment:** Reduce dose by 50% in severe hepatic disease.
* **Renal Impairment:** No dose adjustment is typically needed for intermittent hemodialysis. For significant renal impairment (CrCl < 30 mL/min), consider reducing the dose by 50% if treatment is expected to exceed 4 days.
## Contraindications
* Hypersensitivity to metronidazole or other nitroimidazole derivatives.
* Disulfiram-like reaction with alcohol.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness.
* **Serious:** Peripheral neuropathy, seizures, encephalopathy, aseptic meningitis, Stevens-Johnson syndrome, toxic epidermal necrolysis, pancreatitis, severe hypersensitivity reactions.
## Key Drug Interactions
* **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, tachycardia). Avoid alcohol during treatment and for at least 3 days after.
* **Warfarin:** Increased INR. Monitor INR closely and adjust warfarin dose as needed.
* **Lithium:** Increased lithium levels, potentially leading to toxicity. Monitor lithium levels.
* **Phenytoin, Phenobarbital:** Decreased efficacy of metronidazole.
* **Cyclosporine:** Increased cyclosporine levels. Monitor cyclosporine levels.
## Monitoring
* Monitor for signs and symptoms of neuropathy (numbness, tingling, pain) with prolonged therapy.
* Monitor for signs of C. difficile recurrence.
* Monitor INR if co-administered with warfarin.
* Monitor lithium levels if co-administered with lithium.
## Clinical Pearls
* Administer oral metronidazole with or without food.
* A metallic taste is common and often diminishes with continued therapy.
* Urine may turn a reddish-brown color; this is harmless.
* Avoid concurrent use of alcohol.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols for definitive guidance.*
