Flagyl

# Flagyl ## Overview - **Classification**: Nitroimidazole antibiotic, antiprotozoal. - **Mechanism**: Forms reactive nitro radical anions that damage DNA in susceptible anaerobic bacteria and protozoa, inhibiting nucleic acid synthesis. ## Primary Indications 1. **Anaerobic Bacterial Infections**: Intra-abdominal, skin/soft tissue, gynecologic, bone/joint, CNS. 2. **Protozoal Infections**: Amebiasis, giardiasis, trichomoniasis. 3. **Clostridioides difficile Infection (CDI)**: Mild-to-moderate cases. ## Adult Dosing ### Standard Dosing **Anaerobic Infections (IV/Oral)** - **Dose**: **500 mg** - **Frequency**: Every **8 hours** - **Route**: IV or Oral - **Duration**: 7-10 days (or longer for severe infections) **Trichomoniasis (Oral)** - **Dose**: **2 grams** - **Frequency**: Single dose (or **500 mg** BID for 7 days) - **Route**: Oral - **Duration**: Single dose or 7 days **Amebiasis (Oral)** - **Dose**: **500 mg** to **750 mg** - **Frequency**: Three times a day (TID) - **Route**: Oral - **Duration**: 5-10 days **Clostridioides difficile Infection (Oral)** - **Dose**: **500 mg** - **Frequency**: Three times a day (TID) - **Route**: Oral - **Duration**: 10-14 days ### Dose Adjustments - **Renal Impairment**: No routine adjustment for standard therapy. For ESRD (CrCl < 10 mL/min), consider reducing dose or extending interval. - **Hepatic Impairment**: For severe hepatic dysfunction (Child-Pugh C), reduce dose by **50%**. - **Elderly Patients**: Use caution due to potential decreased hepatic metabolism. Monitor for adverse effects. ## Pediatric Dosing ### Neonates (0-28 days) - **Indication**: Anaerobic infections - **Dose**: **7.5 mg/kg** - **Frequency**: Every **12 hours** (for >7 days old); every **24 hours** (for <7 days old) - **Maximum**: Not formally defined, use lowest effective dose. - **Special Notes**: IV formulation preferred; careful monitoring due to immature hepatic/renal function. ### Infants (1-12 months) - **Indication**: Anaerobic infections - **Dose**: **7.5 mg/kg** - **Frequency**: Every **8 hours** - **Maximum**: **4 grams/day** ### Children (1-12 years) - **Indication**: Anaerobic infections - **Dose**: **7.5 mg/kg** - **Frequency**: Every **8 hours** - **Maximum**: **4 grams/day** (typically **1.5 grams/day** for standard infections) ### Adolescents (13-18 years) - **Dose**: Generally follow **adult dosing** recommendations. - **Maximum**: Follow **adult maximum doses** (e.g., 4 grams/day for severe infections). ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to metronidazole or other nitroimidazole derivatives. - **Absolute**: Disulfiram use within the last **14 days** (risk of psychotic reactions). - **Absolute**: Alcohol consumption during therapy and for **3 days** after (disulfiram-like reaction). ### Common Adverse Effects - **Very Common (>10%)**: Nausea, metallic taste, headache. - **Common (1-10%)**: Vomiting, diarrhea, abdominal cramps, dizziness, dark urine. - **Serious but Rare**: Seizures, peripheral neuropathy (with prolonged use), aseptic meningitis, SJS/TEN, neutropenia. ### Key Drug Interactions - **Alcohol**: Disulfiram-like reaction (flushing, palpitations, nausea, vomiting). Avoid for **3 days** post-treatment. - **Warfarin**: Enhances anticoagulant effect. Monitor INR closely; may need warfarin dose reduction. - **Lithium**: May increase lithium levels and toxicity. Monitor lithium levels. - **Disulfiram**: Risk of psychotic reactions. Avoid concurrent use within **14 days**. - **Busulfan**: May increase busulfan plasma concentrations. Avoid concurrent use. ## Monitoring & Follow-up - **Before Treatment**: Obtain baseline CBC for prolonged therapy or repeated courses. - **During Treatment**: Monitor for CNS toxicity (seizures, numbness/tingling), especially with prolonged or high-dose therapy. - **Clinical Signs**: Watch for new onset dizziness, peripheral neuropathy symptoms, severe rash, fever, sore throat. ## Clinical Pearls - 💡 **Tip 1**: Administer with food to minimize GI upset and the common metallic taste. - 💡 **Tip 2**: Strictly counsel patients to avoid alcohol during treatment and for **3 days** after to prevent severe reactions. - 💡 **Tip 3**: Patients should be aware that urine may turn dark reddish-brown; this is a harmless effect. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.