Bacterial infections:

Indications for: Metronidazole Injection

Susceptible serious anaerobic infections. Surgical prophylaxis.

Adult Dosage:

Infuse over 1hr. Anaerobic infections: 15mg/kg (loading dose), then 7.5mg/kg every 6hrs for 7–10 days; max 4g/24hrs. Bone/joint, lower respiratory tract, endocardium infections: may need to treat longer. Prophylaxis: 15mg/kg 1hr before surgery, then 7.5mg/kg at 6hrs and 12hrs after 1st dose. Severe hepatic impairment: reduce dose by 50%. Hemodialysis: consider dose supplementation after session.

Children Dosage:

Not established.

Metronidazole Injection Contraindications:

Pregnancy (1st trimester for trichomoniasis). Within 2 weeks of disulfiram (possible psychotic reactions). Concomitant alcohol or propylene glycol containing-products during or at least 3 days after treatment. Cockayne syndrome.

Metronidazole Injection Warnings/Precautions:

Discontinue if abnormal neurological symptoms occur. Candidiasis. History of blood dyscrasias. Monitor for leukopenia; do CBCs before, during and after therapy. Hepatic or renal impairment; monitor. Elderly: monitor serum levels. Pregnancy. Nursing mothers: not recommended.

See Also:

Metronidazole Injection Classification:


Metronidazole Injection Interactions:

See Contraindications. May potentiate oral anticoagulants, lithium; monitor. Avoid concomitant busulfan; if needed, adjust busulfan dose and monitor. May be antagonized by phenobarbital, phenytoin, other hepatic enzyme inducers. May impair phenytoin clearance. May be potentiated by cimetidine, other hepatic enzyme inhibitors. IV: may potentiate 5-FU, vecuronium, CYP3A4 substrates (eg, amiodarone, tacrolimus, cyclosporine,carbamazepine, phenytoin, quinidine); monitor. Concomitant drugs with the potential for prolonging the QT interval; caution. May interfere with serum chemistry tests.

Adverse Reactions:

Nausea, headache, anorexia, vomiting, diarrhea, epigastric distress, abdominal cramping, constipation, metallic taste, dysuria, cystitis; seizures, encephalopathy, optic/peripheral neuropathy, aseptic meningitis.


  • Primarily from side-chain oxidation [1-(ßhydroxyethyl)-2-hydroxymethyl-5-nitroimidazole and 2-methyl-5-nitroimidazole-1-ylacetic acid] and glucuronide conjugation, with unchanged metronidazole accounting for approximately 20% of the total. 

Drug Elimination:

  • Renal (60% to 80% of the dose), fecal (6% to 15%).

  • Half-life: 8 hours.

How Supplied:

Tabs—50, 100; Caps 375mg—50; IV—contact supplier