METRO I.V. IN PLASTIC CONTAINER
Clinical safety rating: caution
Comprehensive clinical and safety monograph for METRO I.V. IN PLASTIC CONTAINER (METRO I.V. IN PLASTIC CONTAINER).
Metronidazole exerts its antibacterial and antiprotozoal effects by entering the microbial cell and undergoing reduction by intracellular electron transport proteins, forming reactive metabolites that interact with DNA, causing strand breakage and inhibition of nucleic acid synthesis.
| Metabolism | Hepatic metabolism via oxidation and glucuronidation, primarily by CYP450 enzymes (CYP2A6, CYP3A4). The major metabolites are hydroxymetronidazole and metronidazole glucuronide. |
| Excretion | Renal (60-80% as unchanged drug), fecal (6-15%), biliary (small amount) |
| Half-life | 8 hours (6-12 hours) in adults; prolonged in hepatic impairment |
| Protein binding | <20% bound to plasma proteins |
| Volume of Distribution | 0.25-0.85 L/kg; indicates wide distribution into tissues including CSF |
| Bioavailability | 100% intravenous |
| Onset of Action | Intravenous: immediate |
| Duration of Action | 12-24 hours; dosing interval may be extended in renal impairment |
IV: 500 mg every 6 h or 1 g every 12 h. For severe infections: 750 mg every 6 h. Max 4 g/day.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 10-50 mL/min: 500 mg every 12 h. CrCl <10 mL/min: 500 mg every 24 h. Hemodialysis: dose after dialysis. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B or C: reduce dose by 50% (e.g., 500 mg every 12 h). |
| Pediatric use | Neonates (GA <34 wk): 7.5 mg/kg every 12 h; (GA ≥34 wk): 7.5 mg/kg every 8 h. Infants/children: 10 mg/kg every 6-8 h. Max 4 g/day. |
| Geriatric use | CrCl 10-50 mL/min: 500 mg every 12 h. CrCl <10 mL/min: 500 mg every 24 h. Monitor for neurotoxicity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for METRO I.V. IN PLASTIC CONTAINER (METRO I.V. IN PLASTIC CONTAINER).
| Breastfeeding | Metronidazole is excreted into breast milk with milk-to-plasma ratio of approximately 0.6-1.0. Peak milk concentrations occur 2-4 hours after dose. The American Academy of Pediatrics considers it compatible with breastfeeding, but some sources advise discarding milk for 12-24 hours after a single high dose (2 g) to reduce infant exposure. For standard dosing, benefits likely outweigh risks. |
| Teratogenic Risk | Metronidazole crosses the placenta. In the first trimester, data are conflicting but meta-analyses show no significant increase in major malformations; however, some studies suggest a possible small risk of cleft palate. The CDC and FDA consider it contraindicated in the first trimester unless clearly needed. In the second and third trimesters, it is generally considered safe, but caution is advised near term due to potential neonatal accumulation. |
■ FDA Black Box Warning
Carcinogenicity: Metronidazole has been shown to be carcinogenic in mice and rats. Unnecessary use should be avoided.
| Serious Effects |
["Hypersensitivity to metronidazole or other nitroimidazole derivatives","First trimester of pregnancy (relative contraindication; use only if clearly needed)","Breastfeeding (manufacturer recommends discontinuation of nursing or drug, but AAP considers compatible)","Use with disulfiram (within 2 weeks of disulfiram administration)","Use with alcohol or propylene glycol-containing products (due to disulfiram-like reaction)"]
| Precautions | ["May cause seizures and peripheral neuropathy; discontinue if neurologic symptoms occur.","Use caution in patients with central nervous system disorders.","Blood dyscrasias: Use with caution in patients with history of or current blood dyscrasias.","Hepatic impairment: Dose adjustment may be required.","Carcinogenicity: Avoid prolonged or unnecessary use.","Drug interactions: Potentiation of anticoagulant effect of warfarin; disulfiram-like reaction with alcohol.","Prolonged QT interval: Use with caution with QT-prolonging agents.","Superinfection: May cause overgrowth of Clostridioides difficile."] |
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| Fetal Monitoring | Monitor for signs of hypersensitivity, peripheral neuropathy, and seizures in the mother. No specific fetal monitoring is required beyond standard prenatal care. If used for trichomoniasis in pregnancy, test of cure is recommended after treatment. |
| Fertility Effects | Metronidazole has no known adverse effects on fertility in humans. Animal studies have shown no impairment of fertility at clinically relevant doses. |