Metrogyl%252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252520%252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252528metronidazole%252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252529

# Metronidazole ## Overview Metronidazole is an antibiotic and antiprotozoal agent. ## Primary Indications * Treatment of anaerobic bacterial infections (e.g., intra-abdominal infections, gynecologic infections, skin and soft tissue infections, bone and joint infections, CNS infections, lower respiratory tract infections, endocarditis). * Treatment of trichomoniasis, giardiasis, amebiasis. * Treatment of *Clostridioides difficile* infection (CDI). * Surgical prophylaxis. * Treatment of bacterial vaginosis. * Topical treatment for rosacea. ## Adult Dosing * **Anaerobic Infections:** * Systemic: 500 mg IV or PO every 8 hours. Higher doses may be used for severe infections (e.g., 1 g IV or PO every 8 hours). Duration varies by infection site and severity. * Intra-abdominal infections (in combination therapy): 500 mg IV or PO every 8 hours. * **Trichomoniasis:** * Single dose: 2 grams PO. * Multiple dose: 250 mg PO BID for 7 days or 500 mg PO BID for 7 days. * **Giardiasis:** 250 mg PO TID for 5 days or 400-500 mg PO TID for 5-7 days. * **Amebiasis:** * Invasive intestinal amebiasis: 500-750 mg PO TID for 5-10 days. * Amebic liver abscess: 500-750 mg PO TID for 5-10 days. * ***C. difficile* Infection:** 500 mg PO TID for 10-14 days. *Note: Vancomycin is generally preferred for initial episodes of severe or fulminant CDI.* * **Bacterial Vaginosis:** 500 mg PO BID for 7 days. * **Surgical Prophylaxis:** 1 gram IV infused over 30-60 minutes given within 1 hour before incision, or 500 mg PO every 8 hours for 24 hours starting on the day of surgery. * **Rosacea (Topical):** 0.75% or 1% gel/cream applied to affected areas once or twice daily. ## Pediatric Dosing * **Anaerobic Infections:** * Infants and Children: 7.5 mg/kg IV or PO every 8 hours. Maximum dose 500 mg per dose. Duration varies. * **Giardiasis:** 5 mg/kg PO TID for 5 days. Maximum dose 250 mg per dose. * **Amebiasis:** 10-20 mg/kg/day PO divided into 3 doses for 5-10 days. Maximum dose 750 mg per dose. * **C. difficile Infection:** 7.5 mg/kg PO every 8 hours for 10-14 days. Maximum dose 500 mg per dose. ## Dose Adjustments * **Renal Impairment:** No dose adjustment is typically needed for mild to moderate renal impairment. In severe renal impairment, accumulation may occur; consider reducing the dose. Hemodialysis may necessitate dose adjustments. * **Hepatic Impairment:** In severe hepatic impairment, dose reduction may be necessary due to decreased metabolism. ## Contraindications * Hypersensitivity to metronidazole or other nitroimidazole derivatives. * Use during the first trimester of pregnancy for trichomoniasis (risk vs. benefit considered for other indications). * Concurrent use with disulfiram or alcohol (within 3 days). ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness, dark urine. * **Serious:** Peripheral neuropathy (especially with prolonged use), CNS effects (seizures, encephalopathy, aseptic meningitis), Stevens-Johnson syndrome, toxic epidermal necrolysis, pancreatitis, leukopenia, thrombophlebitis (with IV administration). ## Key Drug Interactions * **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, abdominal cramps, headache). Avoid alcohol during and for at least 3 days after treatment. * **Warfarin:** Increased anticoagulant effect. Monitor INR closely and adjust warfarin dose as needed. * **Lithium:** Metronidazole may increase lithium levels, potentially leading to toxicity. Monitor lithium levels. * **Phenytoin, Phenobarbital:** May decrease metronidazole levels. * **Disulfiram:** Avoid concurrent use; may cause acute psychosis. * **5-Fluorouracil (5-FU) and capecitabine:** Metronidazole may increase the toxicity of these chemotherapy agents. ## Monitoring * **Therapeutic Efficacy:** Clinical improvement of signs and symptoms of infection. * **Adverse Effects:** Monitor for signs of peripheral neuropathy, CNS toxicity, and hypersensitivity reactions. * **Lab Tests:** Complete blood count (CBC) may be monitored for leukopenia, especially with prolonged therapy or high doses. Liver function tests may be considered in patients with hepatic impairment. ## Clinical Pearls * Metronidazole has a bitter, metallic taste which can be mitigated by taking with food or by using flavored preparations if available. * Patients should be advised to avoid alcohol during treatment and for 3 days after the last dose. * IV metronidazole can be administered undiluted or diluted in compatible IV solutions. Avoid solutions containing sodium chloride < 0.75% for dilution due to potential for precipitation. * The risk of peripheral neuropathy increases with prolonged use and higher doses. * Topical metronidazole is used for rosacea and is not absorbed systemically to a significant extent. *** *Disclaimer: This information is intended for healthcare professionals. Always consult the current prescribing information and relevant clinical guidelines for complete details before making treatment decisions.*