FLAGYL I.V. RTU IN PLASTIC CONTAINER
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FLAGYL I.V. RTU IN PLASTIC CONTAINER (FLAGYL I.V. RTU IN PLASTIC CONTAINER).
Metronidazole, a nitroimidazole, exerts bactericidal and antiprotozoal activity via reduction of its nitro group by bacterial or protozoal nitroreductases, forming toxic intermediates that disrupt DNA helical structure and inhibit nucleic acid synthesis.
| Metabolism | Hepatic metabolism via oxidation and glucuronidation; major metabolites include hydroxy-metronidazole (active) and acid metabolites. Enzymes: CYP450 (primarily CYP2A6 and CYP3A4). |
| Excretion | Renal (60-80% as unchanged drug and metabolites), fecal (6-15%), biliary (minor). |
| Half-life | 8 hours (6-10 hours) in adults with normal renal function; prolonged to 12-24 hours in severe hepatic impairment. |
| Protein binding | <20%, primarily to albumin. |
| Volume of Distribution | 0.8-1.2 L/kg; indicates extensive tissue penetration including CNS, bone, and abscesses. |
| Bioavailability | Oral: 100% (nearly complete absorption). |
| Onset of Action | IV: Immediate (peak concentration at end of infusion); oral: 1-2 hours after dose. |
| Duration of Action | 12-24 hours; therapeutic concentration maintained for 8-12 hours after IV dose. |
| Molecular Weight | 171.15 |
Metronidazole: Initial loading dose of 15 mg/kg IV, followed by 7.5 mg/kg IV every 6 hours (max 4 g/day). For surgical prophylaxis: 15 mg/kg IV 1 hour before surgery.
| Dosage form | INJECTABLE |
| Renal impairment | No adjustment required for GFR >10 mL/min. For GFR <10 mL/min: administer every 12 hours. Hemodialysis: administer normal dose after dialysis; no supplemental dose needed. Peritoneal dialysis: administer normal dose every 12 hours. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50% (e.g., 7.5 mg/kg every 12 hours). Child-Pugh C: use contraindicated or reduce dose to 7.5 mg/kg every 24 hours with close monitoring. |
| Pediatric use | Neonates (0-6 weeks): 15 mg/kg IV loading, then 7.5 mg/kg IV every 12 hours. Infants/children (>6 weeks): 15 mg/kg IV loading, then 7.5 mg/kg IV every 6 hours (max 4 g/day). For surgical prophylaxis: 15 mg/kg IV 1 hour before surgery. |
| Geriatric use | No specific dose adjustment based solely on age. Monitor renal function and adjust if GFR <10 mL/min. Consider reduced hepatic clearance; use lowest effective dose and monitor for adverse effects. |
| 1st trimester | Avoid unless essential; metronidazole crosses placenta and is associated with possible teratogenic risk in some studies; use only for serious infections. |
| 2nd trimester | Use only if clearly indicated; no proven fetal harm but caution due to placental transfer. |
| 3rd trimester | Use only if clearly indicated; no proven fetal harm but caution due to placental transfer. |
Clinical note
Comprehensive clinical and safety monograph for FLAGYL I.V. RTU IN PLASTIC CONTAINER (FLAGYL I.V. RTU IN PLASTIC CONTAINER).
| Placental transfer | Readily crosses the placenta; achieves fetal serum concentrations similar to maternal levels. |
| Breastfeeding | Metronidazole is excreted into breast milk; after a single 2 g dose, withhold breastfeeding for 12-24 hours to reduce infant exposure; long-term therapy may require monitoring of infant for diarrhea or candidiasis. |
■ FDA Black Box Warning
Carcinogenicity: Metronidazole has been shown to be carcinogenic in mice and rats. Its use should be reserved for conditions described in the indications. Unnecessary use should be avoided.
| Serious Effects |
Hypersensitivity to metronidazole or other nitroimidazole derivativesFirst trimester of pregnancy (relative, but often considered absolute for non-essential use)Active neurological disorders (e.g., epilepsy) due to risk of CNS toxicity
| Precautions | Carcinogenicity risk (animal data; avoid unnecessary use), Seizures and peripheral neuropathy (discontinue if abnormal neurologic signs occur), Hepatic impairment: dose adjustment may be required; caution in severe liver disease, Renal impairment: accumulation of metabolites; monitor for toxicity, Blood dyscrasias: history of or current; monitor CBC with prolonged therapy, Candidiasis: may cause overgrowth; treat appropriately, Disulfiram-like reaction with alcohol: avoid alcohol during and for 48 hours after therapy, Drug interactions: warfarin (increased INR), lithium (increased toxicity), CYP450 inducers/inhibitors, Pregnancy: reserve for serious infections; use in trichomoniasis only if no alternative, Lactation: discontinue breastfeeding or drug, considering importance to mother |
Loading safety data…
| Lactation Rating | L3 - Moderately Safe (previously L2 but updated due to potential toxicity at high doses) |
| Teratogenic Risk | Metronidazole crosses the placenta. First trimester: Avoid use; data suggest possible teratogenic risk (cleft palate), though not conclusively. Second and third trimesters: Generally considered safe for short-term treatment of bacterial vaginosis or trichomoniasis; no evidence of increased major malformations. However, use only if clearly needed. |
| Fetal Monitoring | Monitor maternal liver function, renal function, and CBC especially with prolonged therapy. Infant monitoring for signs of metronidazole toxicity (e.g., diarrhea, candidiasis) if breastfeeding occurs. No specific fetal monitoring required but routine ultrasound may be considered if used in early gestation. |
| Fertility Effects | No significant adverse effects on fertility reported in animal studies or human data. Possible reversible decrease in sperm motility with high doses in males, but clinical significance is unclear. |
| Food/Dietary |
| No direct food interactions, but alcohol and alcohol-containing foods (e.g., sauces, vinegar, fermented products) must be strictly avoided during therapy and for 48 hours after completion due to risk of disulfiram-like reaction. |
| Clinical Pearls | Flagyl IV RTU (metronidazole) is a nitroimidazole antibiotic used for anaerobic infections and protozoal diseases. Avoid alcohol during therapy and for 48 hours after due to disulfiram-like reaction. Infuse slowly over 30-60 minutes to minimize infusion reactions. Monitor for peripheral neuropathy and CNS effects with prolonged use. Use with caution in hepatic impairment; adjust dose in severe liver disease. May cause metallic taste. Do not mix with other drugs in the same IV line. Contraindicated in first trimester of pregnancy unless life-threatening. |
| Patient Advice | Do not drink alcohol or use products containing alcohol during treatment and for at least 48 hours after the last dose; this can cause severe nausea, vomiting, flushing, and headache. · This medication may cause a metallic taste in the mouth, which is temporary. · If you experience numbness, tingling, or pain in your hands or feet, or any signs of an allergic reaction, contact your healthcare provider immediately. · For IV administration, the infusion site should be monitored for signs of redness, swelling, or pain. · Take the medication exactly as prescribed; do not stop without consulting your doctor. · Inform your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. |