Metrogyl (metronidazole)

# Metrogyl (metronidazole) ## Overview Metronidazole is an antibiotic and antiprotozoal agent effective against anaerobic bacteria and certain parasites. ## Primary Indications * **Bacterial vaginosis:** Treatment of bacterial vaginosis. * **Trichomoniasis:** Treatment of symptomatic trichomoniasis. * **Giardiasis:** Treatment of symptomatic giardiasis. * **Amebiasis:** Treatment of amebiasis (intestinal and extraintestinal). * **Anaerobic bacterial infections:** Treatment of serious anaerobic bacterial infections, often as part of combination therapy (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 *Clostridioides difficile*-associated diarrhea (CDAD). * **Surgical prophylaxis:** Prophylaxis against anaerobic infection in specific surgical procedures (e.g., colorectal surgery). ## 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, one applicatorful (5g) inserted vaginally 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. * **Giardiasis:** 250 mg orally three times daily for 5 days, OR 500 mg orally twice daily for 7-10 days. * **Amebiasis (Intestinal):** 500-750 mg orally three times daily for 5-10 days. * **Amebiasis (Extra-intestinal):** 500-750 mg orally three times daily for 5-10 days. * **Anaerobic Bacterial Infections:** 500 mg intravenously or orally every 8 hours. Duration varies based on severity and site of infection. Max oral dose is generally 4 g daily. * **Pseudomembranous Colitis (CDAD):** 500 mg orally three times daily. Duration is typically 10-14 days. * **Surgical Prophylaxis:** 1 g orally or intravenously 1 hour before surgery, followed by 500 mg orally or intravenously every 8 hours for up to 24 hours post-operatively. ## Pediatric Dosing Dosing in pediatrics is often based on weight and the specific indication. Consult specific guidelines or product information for precise dosing. * **Giardiasis:** 5 mg/kg/dose orally three times daily for 5 days. Maximum dose 250 mg per dose. * **Amebiasis (Intestinal):** 35-50 mg/kg/day orally divided into three doses for 5-10 days. Maximum dose 750 mg per dose. * **Anaerobic Bacterial Infections:** 7.5 mg/kg/dose intravenously or orally every 8 hours. Maximum dose 500 mg per dose. ## Dose Adjustments * **Renal Impairment:** No dose adjustment is generally required. Hemodialysis may remove metronidazole; consult guidelines for potential re-dosing. * **Hepatic Impairment:** Dose reduction may be necessary in severe hepatic impairment. ## Contraindications * Known hypersensitivity to metronidazole or other nitroimidazole derivatives. * First trimester of pregnancy (for systemic use, although risks are debated). ## Adverse Effects Common: Nausea, vomiting, diarrhea, abdominal pain, metallic taste, headache, dizziness. Less Common/Serious: Peripheral neuropathy (especially with prolonged use), seizures, encephalopathy, Stevens-Johnson syndrome, candidiasis, anorexia, dark urine. ## Key Drug Interactions * **Alcohol:** Disulfiram-like reaction (severe nausea, vomiting, flushing, headache). Advise patients to avoid alcohol during treatment and for at least 3 days after completion. * **Warfarin:** Increased anticoagulant effect. Monitor INR closely and adjust warfarin dose as needed. * **Lithium:** Increased lithium levels, potentially leading to toxicity. Monitor lithium levels. * **Phenytoin/Phenobarbital:** May decrease metronidazole levels. * **Cyclosporine:** May increase cyclosporine levels. ## Monitoring * Monitor for signs and symptoms of infection resolution. * Assess for adverse effects, particularly peripheral neuropathy and CNS symptoms with prolonged therapy. * Monitor INR if co-administered with warfarin. * Monitor lithium levels if co-administered with lithium. ## Clinical Pearls * A metallic taste is a common and expected side effect. * Avoid alcohol during and for at least 72 hours after completing therapy. * For prolonged therapy, monitor for peripheral neuropathy. * Intravenous administration is often preferred for severe infections. * Can be used in combination with other antibiotics for broader coverage. *** *This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant clinical guidelines for definitive patient care decisions. Dosing may vary based on specific clinical scenarios and local protocols.*