Metrogyl%25252525252525252525252525252525252525252525252525252525252525252520%25252525252525252525252525252525252525252525252525252525252525252528metronidazole%25252525252525252525252525252525252525252525252525252525252525252529

# Metronidazole (Metrogyl) ## Overview Metronidazole is an antimicrobial agent effective against anaerobic bacteria and certain protozoa. ## Primary Indications * **Bacterial Vaginosis:** Treatment of vaginal infections. * **Trichomoniasis:** Treatment of sexually transmitted infections. * **Amebiasis:** Treatment of intestinal and extraintestinal amebiasis. * **Giardiasis:** Treatment of intestinal protozoal infections. * **Anaerobic Bacterial Infections:** Treatment of infections caused by susceptible anaerobic organisms, including intra-abdominal infections, skin and skin structure infections, gynecologic infections, bone and joint infections, CNS infections, and lower respiratory tract infections. * **Pseudomembranous Colitis (C. difficile infection):** Alternative agent for mild to moderate disease. * **Prophylaxis:** Surgical prophylaxis in specific procedures (e.g., colorectal surgery). * **H. pylori eradication:** Part of combination therapy. ## Adult Dosing * **Bacterial Vaginosis:** 500 mg orally twice daily for 7 days, or a single 2 g dose orally. Alternatively, 0.75% vaginal gel inserted intravaginally once daily for 5 days. * **Trichomoniasis:** 2 g single oral dose, or 250 mg orally three times daily for 7 days, or 375 mg orally twice daily for 7 days. * **Amebiasis (Intestinal):** 500-675 mg orally three times daily for 5-10 days. * **Amebiasis (Extra-intestinal):** 500-675 mg orally three times daily for 5-10 days. * **Giardiasis:** 250 mg orally three times daily for 5 days, or a single 2 g dose orally. * **Anaerobic Bacterial Infections:** 500 mg IV or orally every 8 hours. Dosing duration depends on severity and clinical response, typically 7-10 days. * **Pseudomembranous Colitis (C. difficile infection):** 250-500 mg orally every 6-8 hours for 10-14 days. * **Surgical Prophylaxis (Colorectal):** 1 g IV given within 12 hours before surgery, followed by 500 mg IV or orally every 8 hours for up to 24 hours postoperatively. * **H. pylori Eradication:** Typically 500 mg orally twice daily in combination with other agents for 10-14 days. ## Pediatric Dosing Dosing varies significantly based on indication and weight. Consult specific pediatric guidelines. * **Giardiasis:** 15 mg/kg/day orally divided into 3 doses for 5 days, not to exceed 250 mg per dose or 2 g total per day. * **Amebiasis:** 35-50 mg/kg/day orally divided into 3 doses for 5-10 days, not to exceed 750 mg per dose or 2.25 g total per day. * **Anaerobic Bacterial Infections:** 7.5 mg/kg/dose IV or orally every 8 hours. ## Dose Adjustments * **Hepatic Impairment:** Use with caution. May require dose reduction in severe hepatic impairment. Data is limited. * **Renal Impairment:** No dose adjustment generally needed for routine hemodialysis. For significant renal impairment, monitor drug levels if prolonged therapy is anticipated. ## Contraindications * Hypersensitivity to metronidazole or other nitroimidazole derivatives. * First trimester of pregnancy (relative contraindication, risk vs. benefit). * Concomitant use of disulfiram. ## Adverse Effects * **Gastrointestinal:** Nausea, vomiting, diarrhea, abdominal pain, metallic taste. * **Neurologic:** Dizziness, headache, peripheral neuropathy (especially with prolonged use), seizures (rare). * **Hematologic:** Leukopenia, neutropenia. * **Dermatologic:** Rash, urticaria, pruritus. * **Other:** Darkened urine, candidiasis. ## Key Drug Interactions * **Alcohol:** Disulfiram-like reaction (flushing, nausea, vomiting, tachycardia, headache). Avoid alcohol during and for at least 3 days after treatment. * **Warfarin:** Potentiates anticoagulant effect. Monitor INR closely and adjust warfarin dose as needed. * **Lithium:** May increase lithium levels. Monitor lithium levels. * **Phenytoin/Phenobarbital:** May decrease metronidazole levels. * **Disulfiram:** Concurrent use is contraindicated due to potential for psychotic reactions. * **Fluorouracil:** Metronidazole may increase fluorouracil toxicity. ## Monitoring * Clinical signs and symptoms of infection. * Complete blood count (CBC) periodically, especially with prolonged therapy. * Neurologic status. * For H. pylori, assess for eradication via appropriate testing after treatment completion. ## Clinical Pearls * Advise patients to avoid alcohol during and for 72 hours after therapy. * A metallic taste is common and expected. * Neurologic side effects can be dose- and duration-dependent; counsel patients to report numbness, tingling, or dizziness. * Use in pregnancy: Generally avoided in the first trimester unless benefits outweigh risks; used cautiously in the second and third trimesters. *** *Disclaimer: This information is for clinical reference only. Always consult the most current prescribing information and institutional protocols before administering medications.*