Recommended Doses of Cefuroxime and Metronidazole for Adults
For an adult patient with normal renal and hepatic function, the standard dose of cefuroxime is 750–1500 mg IV every 8 hours (or 250–500 mg orally twice daily for oral formulations), and metronidazole is 500 mg IV every 8 hours or 1000 mg (1 g) as a single prophylactic dose in surgical settings. 1, 2, 3
Cefuroxime Dosing
Intravenous (IV) Administration
- Standard IV dose: 750 mg every 8 hours for most infections 1
- Severe infections (e.g., pneumonia, bacteremia): 1500 mg IV every 8 hours 4, 5
- Surgical prophylaxis: 1500 mg IV as a single dose, with re-injection of 750 mg every 2 hours intraoperatively if surgery exceeds 2 hours 1, 4, 3
The every-8-hour dosing interval is critical because cefuroxime has a short half-life (approximately 1.4 hours in patients with normal renal function), and maintaining consistent therapeutic serum concentrations requires three-times-daily administration for serious infections 2, 6, 5
Oral Administration (Cefuroxime Axetil)
- Standard oral dose: 250–500 mg twice daily 2
- Severe infections (e.g., pneumonia): 500 mg twice daily 2
- Maximum daily dose: 4000 mg/day 2
Oral cefuroxime axetil should be taken with food to enhance absorption 2
Metronidazole Dosing
Intravenous Administration
- Standard IV dose for anaerobic infections: 500 mg IV every 8 hours 1
- Surgical prophylaxis (colorectal surgery): 1500 mg IV infused over 1 hour as a single dose prior to surgery, with additional doses needed if surgery exceeds 2 hours 1, 3
Oral Administration
- Standard oral dose: 500 mg three times daily or 400 mg three times daily, depending on the indication 1
The half-life of metronidazole in patients with normal hepatic and renal function is approximately 5.9 hours, allowing for every-8-hour dosing 7
Combined Prophylactic Regimen (Colorectal Surgery)
For colorectal surgery prophylaxis, administer 1500 mg cefuroxime IV over 15 minutes and 1500 mg metronidazole IV over 1 hour prior to incision. 3
- Short surgeries (≤2 hours): A single dose of each antibiotic is adequate 3
- Longer surgeries (>2 hours): Re-dose cefuroxime 750 mg every 2 hours intraoperatively; metronidazole typically does not require re-dosing unless surgery exceeds 4 hours or the patient weighs >90 kg 1, 3
Key Clinical Considerations
Renal Function Impact
- Cefuroxime elimination is highly dependent on creatinine clearance (CrCl). In patients with normal renal function (CrCl >85 mL/min), no dose adjustment is needed 6
- Patients with CrCl 50–84 mL/min can receive standard doses, but those with CrCl <50 mL/min require dose reduction or interval extension 6
Hepatic Function Impact
- Metronidazole clearance is significantly reduced in hepatic insufficiency. Patients with liver disease have a prolonged half-life (11.2 hours vs. 5.9 hours in normal patients) and require dose reduction 7
- Cefuroxime does not require dose adjustment in hepatic impairment 6
Common Pitfalls
- Avoid underdosing cefuroxime in serious infections: The 750 mg every 8 hours regimen may be insufficient for pathogens with higher MICs (e.g., E. coli, K. pneumoniae); use 1500 mg every 8 hours for these organisms 5
- Do not extend dosing intervals beyond 8 hours for IV cefuroxime in serious infections, as this compromises time above MIC (T>MIC), the key pharmacodynamic parameter for beta-lactams 2, 5
- Metronidazole does not require renal dose adjustment unless there is concurrent hepatic impairment, but metabolites accumulate in renal failure 7