Metrogyl%25252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252520%25252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252528metronidazole%25252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252529

# Metronidazole ## Overview Metronidazole is an antibiotic and antiprotozoal agent effective against anaerobic bacteria and certain protozoa. ## 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, central nervous system infections, lower respiratory tract infections, endocarditis) * *Clostridioides difficile* infection (CDI) * Surgical prophylaxis in colorectal surgery * *Helicobacter pylori* eradication (in combination regimens) ## Adult Dosing * **Bacterial vaginosis:** 500 mg orally twice daily for 7 days, or 500 mg orally once daily for 7 days, or 2 g orally in a single dose, or 1% vaginal gel applied intravaginally once daily for 5 days. * **Trichomoniasis:** 2 g orally in a single dose, or 250 mg orally three times daily for 7 days, or 375 mg orally twice daily for 7 days. * **Amebiasis:** * *Invasive amebiasis:* 500-750 mg orally three times daily for 5-10 days. * *Asymptomatic cyst passer:* 250 mg orally three times daily for 10 days. * **Giardiasis:** 250 mg orally three times daily for 5-7 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 site and severity. Typical duration is 7-14 days, but may be longer. * **CDI:** * Initial episode: 500 mg orally three times daily for 10-14 days. (Note: Vancomycin is generally preferred for initial episodes of non-severe CDI). * Recurrent episodes: Dosing depends on previous treatment and local guidelines. * **Surgical prophylaxis:** 1 g IV 1-2 hours before surgery, or 500 mg orally every 8 hours starting the day before surgery and continuing for 24 hours. * ***H. pylori* eradication:** Typically 250-500 mg orally twice daily in combination with other agents. Duration varies by regimen (e.g., 10-14 days). ## Pediatric Dosing Dosing is weight-based and depends on the indication. Consult specific pediatric infectious disease guidelines. * **General anaerobic infections:** 15-30 mg/kg/day orally or IV divided every 8 hours, not to exceed adult maximum doses. * **Intestinal amebiasis:** 35-50 mg/kg/day orally divided every 8 hours for 5-10 days. * **Giardiasis:** 15 mg/kg/day orally divided every 8 hours for 5-7 days, maximum 250 mg/dose. * **Bacterial vaginosis:** Not typically used in pediatric patients. * **Trichomoniasis:** Not typically used in pediatric patients. ## Dose Adjustments * **Renal impairment:** No dose adjustment generally needed for oral or IV doses, but prolonged use may require adjustment if accumulation occurs. Hemodialysis may necessitate dose adjustment. * **Hepatic impairment:** Use with caution. Consider reducing dose in severe hepatic disease. ## Contraindications * Hypersensitivity to metronidazole or other nitroimidazole derivatives. * Concurrent use with disulfiram or alcohol (within 3 days of last dose). ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, metallic taste, abdominal pain, headache, anorexia. * **Serious:** Peripheral neuropathy (especially with prolonged or high-dose use), seizures, encephalopathy, Stevens-Johnson syndrome, hypersensitivity reactions, pancreatitis, dark urine. * **Disulfiram-like reaction with alcohol:** Flushing, headache, nausea, vomiting, tachycardia. ## Key Drug Interactions * **Alcohol:** Disulfiram-like reaction. Avoid alcohol during and for at least 3 days after treatment. * **Disulfiram:** Risk of psychosis, confusion. Avoid concurrent use. * **Warfarin:** Metronidazole may enhance the 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 efficacy. * **5-Fluorouracil:** Metronidazole may increase toxicity of 5-FU. ## Monitoring * Signs and symptoms of infection. * Liver function tests (especially with prolonged use or hepatic impairment). * Complete blood count (especially with prolonged use). * Neurological status for signs of peripheral neuropathy or central nervous system effects. * INR if patient is on warfarin. * Lithium levels if patient is on lithium. ## Clinical Pearls * Take oral metronidazole with food to minimize gastrointestinal upset. * Advise patients to avoid alcohol during treatment and for 3 days after the last dose due to the potential for a disulfiram-like reaction. * Metallic taste is a common and expected side effect. * Urine may turn a reddish-brown color; this is harmless. * Treatment for *H. pylori* and CDI often involves specific protocols and combination therapies. *** **Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the current prescribing information and relevant guidelines for the most up-to-date and complete information before making any treatment decisions.