Metrogyl%252520%252528metronidazole%252529

# Metrogyl (metronidazole) ## Overview Metronidazole is a nitroimidazole antibiotic with activity against anaerobic bacteria and certain protozoa (e.g., *Trichomonas*, *Giardia*, *Entamoeba*). It is available in oral, intravenous, topical, and vaginal formulations. ## Primary Indications - Anaerobic bacterial infections (intra-abdominal, pelvic, skin/soft tissue, bone/joint, CNS abscess) - Antibiotic-associated diarrhea (*Clostridioides difficile* infection) - Trichomoniasis, giardiasis, amebiasis - Bacterial vaginosis - Perioperative prophylaxis (colorectal surgery, appendectomy) ## Adult Dosing - **Anaerobic infection (IV/oral):** 500 mg every 8 hours. Severe infection: 1 g IV loading dose, then 500 mg IV every 6 hours. Max IV rate: 1 g over 1 hour. - **C. difficile infection (oral):** 500 mg three times daily for 10–14 days. IV is less effective; use only if oral route not possible. - **Trichomoniasis:** 2 g single oral dose (or 500 mg twice daily for 7 days). - **Giardiasis:** 250 mg three times daily for 5–7 days. - **Amebiasis:** 750 mg three times daily for 5–10 days. - **Bacterial vaginosis:** 500 mg twice daily for 7 days (oral) or 0.75% gel 5 g intravaginally once daily for 5 days. ## Pediatric Dosing - **Anaerobic infection (IV/oral):** 15–30 mg/kg/day divided every 8 hours. Max: 4 g/day. - **C. difficile (oral):** 30 mg/kg/day divided every 6–8 hours, for 10–14 days. Max: 2 g/day. - **Giardiasis:** 15 mg/kg/day divided three times daily for 5–7 days. Max: 750 mg/day. - **Amebiasis:** 35–50 mg/kg/day divided three times daily for 10 days. Max: 2 g/day. - **Trichomoniasis in adolescents:** 2 g single dose (same as adult). *Dosing for neonates and infants <8 weeks: 15 mg/kg/day divided every 12 hours (IV/oral). Use with caution; adjust based on gestational age and weight.* ## Dose Adjustments - **Hepatic impairment:** Severe liver disease (Child-Pugh C): reduce dose by 50–75% or extend interval. Mild-moderate: no adjustment generally needed. - **Renal impairment:** No dose adjustment for standard dosing. For C. difficile, consider longer interval if eGFR <10 mL/min. Metronidazole and its metabolites are removed by hemodialysis; supplement after dialysis if needed. - **Elderly:** No specific adjustment, but monitor for neurotoxicity. ## Contraindications - Hypersensitivity to metronidazole or other nitroimidazoles - First trimester of pregnancy (avoid unless no alternative; use with caution in second/third trimester) - Concomitant use with disulfiram (psychotic reactions) or with alcohol-containing products (disulfiram-like reaction) ## Adverse Effects - **Common:** Metallic taste, nausea, headache, dry mouth, dark urine (harmless). - **Serious:** Peripheral neuropathy (dose-dependent, reversible if caught early), CNS toxicity (seizures, encephalopathy, ataxia), pancreatitis, hepatic toxicity (rare), leukopenia, C. difficile overgrowth. - **Long-term use (>2–4 weeks):** Monitor for neurotoxicity. ## Key Drug Interactions - **Warfarin:** Potentiates anticoagulant effect (monitor INR). - **Disulfiram:** Psychotic reactions (avoid co-administration). - **Alcohol:** Disulfiram-like reaction (flushing, vomiting, headache) – avoid alcohol during therapy and for 48 hours after last dose. - **Lithium:** May increase lithium levels (monitor). - **Phenytoin/Phenobarbital:** Decreased metronidazole levels; increased phenytoin levels. - **Cimetidine:** May increase metronidazole levels (monitor for toxicity). ## Monitoring - Baseline CBC, liver function tests, and renal function (especially with prolonged therapy). - Clinical signs of infection resolution. - Neurologic symptoms (paresthesia, ataxia, confusion) – discontinue if develop. - INR in patients on warfarin. - Periodic CBC if therapy >2 weeks. ## Clinical Pearls - **Bioavailability:** Oral absorption is >90%; IV and oral dosing are generally equivalent for most infections. - **C. difficile:** Metronidazole is first-line for mild-moderate disease; oral vancomycin is preferred for severe or recurrent cases. - **Anaerobic coverage:** Excellent against *Bacteroides fragilis* and *Clostridium* species. Not active against aerobic bacteria. - **Pregnancy:** Avoid in first trimester; use only if clearly needed in second/third trimester. Topical/vaginal forms have minimal systemic absorption. - **Disulfiram-like reaction:** Educate patients to avoid all alcohol (including mouthwash, cough syrups) during and for 48 hours after last dose. - **IV formulation:** Contains sodium; caution in patients with heart failure or hypertension. --- *Educational disclaimer: This information is for educational purposes and does not replace clinical judgment. Always verify current prescribing information, local guidelines, and formulary availability before use. Dosing may vary based on indication, patient factors, and local protocols.*