Metrogyl%252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252520%252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252528metronidazole%252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252529

# Metronidazole (Metrogyl) ## Overview Metronidazole is a nitroimidazole antibiotic effective against anaerobic bacteria and certain protozoa. ## Primary Indications * **Bacterial Vaginosis:** Treatment of bacterial vaginosis. * **Trichomoniasis:** Treatment of *Trichomonas vaginalis* infection. * **Amebiasis:** Treatment of amebiasis. * **Giardiasis:** Treatment of *Giardia lamblia* infection. * **Anaerobic Bacterial Infections:** Treatment of serious infections caused by susceptible anaerobic bacteria (e.g., intra-abdominal infections, skin and soft tissue infections, gynecologic infections, bone and joint infections, CNS infections, lower respiratory tract infections, endocarditis). * **Pseudomembranous Colitis:** Treatment of *Clostridium difficile*-associated diarrhea (CDAD). * **Surgical Prophylaxis:** Perioperative prophylaxis in specific colorectal surgeries. * **Helicobacter pylori Eradication:** Part of multi-drug regimens for *H. pylori* eradication. ## Adult Dosing * **Bacterial Vaginosis:** 500 mg orally twice daily for 7 days, OR 2 g orally as a single dose, OR 0.75% vaginal gel applied intravaginally once daily for 5 days. * **Trichomoniasis:** 2 g orally as a single dose, OR 250 mg orally three times daily for 7 days, OR 375 mg orally twice daily for 7 days. * **Amebiasis (Intestinal and Invasive):** 500-675 mg orally three to four times daily for 5-10 days. * **Giardiasis:** 250 mg orally three times daily for 5 days, OR 2 g orally once daily for 3 days. * **Anaerobic Bacterial Infections:** 500 mg IV or orally every 8 hours. Duration varies by infection severity and site, typically 7-14 days. For severe infections, doses up to 1 g IV every 8 hours may be used, not to exceed 4 g daily. * **CDAD:** 500 mg orally every 8 hours for 10-14 days. IV administration may be necessary if oral route is not feasible. * **Surgical Prophylaxis (Colorectal):** 1 g IV as a single dose given 30-60 minutes before surgery, or 500 mg orally every 8 hours starting 1-2 days before surgery and continuing postoperatively. * **H. pylori Eradication:** Part of combination therapy, typically 500 mg orally twice daily for 10-14 days. ## Pediatric Dosing Dosing is weight-based and depends on the indication. Consult specific guidelines for precise pediatric dosing. General examples: * **Giardiasis:** 5 mg/kg/dose orally three times daily for 5 days, not to exceed 250 mg/dose (max 750 mg/day). * **Intestinal Amebiasis:** 35-50 mg/kg/day orally divided into three doses for 5-10 days. * **Anaerobic Infections:** 7.5 mg/kg/dose IV or orally every 8 hours. Usual pediatric dose 20-30 mg/kg/day divided every 8 hours. Maximum daily dose for children is generally 4 g. ## Dose Adjustments * **Renal Impairment:** No dose adjustment generally recommended for the parent drug. However, the active metabolite (hydroxy-metronidazole) can accumulate in severe renal failure. For hemodialysis patients, administer a supplemental dose after dialysis. * **Hepatic Impairment:** No specific dose adjustment is recommended, but caution is advised. For severe hepatic disease, consider reducing the maintenance dose. ## Contraindications * Hypersensitivity to metronidazole or other nitroimidazole derivatives. * First trimester of pregnancy (relative contraindication; benefit vs. risk assessment needed). * Concomitant use of disulfiram or alcohol due to disulfiram-like reaction. ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, metallic taste, glossitis, stomatitis, headache, dizziness, rash, pruritus. * **Serious:** Peripheral neuropathy (especially with prolonged use), seizures, encephalopathy, aseptic meningitis, Stevens-Johnson syndrome, toxic epidermal necrolysis, pancreatitis, neutropenia, thrombophlebitis (with IV administration). * **Disulfiram-like reaction:** Flushing, headache, nausea, vomiting, abdominal cramps, chest pain when taken with alcohol. ## Key Drug Interactions * **Alcohol:** Disulfiram-like reaction. Avoid alcohol during treatment and for at least 3 days after. * **Disulfiram:** Can cause psychosis, confusion. Avoid concurrent use. * **Warfarin:** Increased anticoagulant effect. Monitor INR closely and adjust warfarin dose as needed. * **Lithium:** May increase lithium levels, leading to toxicity. Monitor lithium levels. * **Phenytoin, Phenobarbital:** May decrease metronidazole levels. * **5-Fluorouracil (5-FU):** Metronidazole may increase 5-FU toxicity. ## Monitoring * Monitor for signs and symptoms of peripheral neuropathy (numbness, tingling, pain). * Monitor for signs of CNS toxicity (seizures, encephalopathy). * Monitor for signs of hypersensitivity reactions. * Monitor CBC if prolonged therapy is anticipated or in patients with history of blood dyscrasias. * Monitor INR if co-administered with warfarin. * Monitor lithium levels if co-administered with lithium. ## Clinical Pearls * Metronidazole has a metallic taste which can be bothersome. * Advise patients to avoid alcohol during and for at least 72 hours after treatment. * IV formulation can cause thrombophlebitis; rotate IV sites frequently. * Consider using oral metronidazole for CDAD if the patient can tolerate oral intake. * Urine may turn a reddish-brown color. *** *This information is for educational purposes only and does not substitute for professional medical advice. Always verify current prescribing information with the most up-to-date product monographs or reliable clinical resources before making any treatment decisions.*