Metrogyl%25252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252520%25252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252528metronidazole%25252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252529

# Metronidazole (Metrogyl) ## Overview Metronidazole is an antibiotic and antiprotozoal agent effective against anaerobic bacteria and certain protozoa. ## 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, bacterial vaginosis). * Treatment of protozoal infections (e.g., trichomoniasis, amebiasis, giardiasis). * Surgical prophylaxis. ## Adult Dosing * **Anaerobic Infections:** 500 mg IV or PO every 8 hours. Duration varies by infection severity, typically 7-14 days. Maximum IV dose generally 4 g/day. * **Bacterial Vaginosis:** 500 mg PO BID for 7 days, or 500 mg PO single dose, or 0.75% vaginal gel applied intravaginally once daily for 5 days. * **Trichomoniasis:** 2 g PO single dose, or 250 mg PO TID for 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. * **Giardiasis:** 250 mg PO TID for 5-7 days. * **Surgical Prophylaxis (Colorectal):** 1 g IV 1-2 hours before surgery, or 500 mg IV or PO every 8 hours starting before surgery and continuing for up to 24 hours postoperatively. ## Pediatric Dosing * **Anaerobic Infections:** 15 mg/kg PO or IV as a loading dose, followed by 7.5 mg/kg PO or IV every 8 hours. Duration varies. Maximum dose typically 4 g/day. * **Bacterial Vaginosis (if indicated):** Not generally recommended in pediatric patients. * **Trichomoniasis:** Not generally recommended in pediatric patients. * **Amebiasis:** 35-50 mg/kg/day PO or IV divided into 3 doses for 5-10 days. Maximum 750 mg/dose or 4 g/day. * **Giardiasis:** 5 mg/kg PO TID for 5 days. Maximum 250 mg/dose. ## Dose Adjustments * **Renal Impairment:** No dose adjustment generally needed for mild to moderate renal impairment. Significant accumulation may occur in severe impairment, but data is limited. Consider extending interval or reducing dose if prolonged therapy is anticipated. * **Hepatic Impairment:** Use with caution. Reduce total daily dose by 30-50% in severe hepatic impairment. ## Contraindications * Known hypersensitivity to metronidazole or other nitroimidazole derivatives. * First trimester of pregnancy (relative contraindication, consider risks/benefits). ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness. * **Serious:** Peripheral neuropathy (especially with prolonged use), seizures, encephalopathy, aseptic meningitis, Stevens-Johnson syndrome, neutropenia. * **Disulfiram-like reaction:** Severe nausea, vomiting, flushing, and palpitations when taken with alcohol. ## Key Drug Interactions * **Alcohol:** Disulfiram-like reaction. Advise patients to 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:** May increase lithium levels, potentially leading to toxicity. Monitor lithium levels. * **Phenytoin, Phenobarbital:** May decrease metronidazole levels. * **Cyclosporine:** May increase cyclosporine levels. * **5-Fluorouracil (5-FU):** May increase toxicity of 5-FU. ## Monitoring * Assess for signs and symptoms of infection resolution. * Monitor for adverse effects, particularly neurological symptoms and signs of peripheral neuropathy. * Monitor complete blood count (CBC) periodically for prolonged therapy or high doses. * Monitor lithium and warfarin levels if co-administered. ## Clinical Pearls * Advise patients to avoid alcohol during and for 3 days after metronidazole therapy due to the disulfiram-like reaction. * A metallic taste is common and usually resolves after treatment completion. * For vaginal gel, instruct patients on proper administration. * IV metronidazole has a characteristic yellow/orange color; this is normal. *** *Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for definitive patient care decisions.*