Cefoxitin !
A second-generation intravenous cephamycin active against anaerobes such as Bacteroides fragilis; used in mixed abdominal and pelvic infections.
Updated 2026-11-01
The figure shows E. coli PBP5 (a DD-carboxypeptidase) in an acyl-enzyme complex with cefoxitin.
Mechanism of action
Cefoxitin is a cephamycin, with a methoxy group at position 7 of the core; it is stable to many β-lactamases, including those of Bacteroides fragilis, and more stable than other cephalosporins to ESBLs. It acylates the PBPs and stops wall synthesis. It covers susceptible gram-positive cocci, enteric bacteria and anaerobes, but is less active against H. influenzae and does not cover enterococci or Pseudomonas.
- Resists anaerobe β-lactamases
- Acylates the PBPs of Bacteroides and enteric bacteria
- Peptidoglycan cross-linking stops
- The bacterium lyses
Pharmacokinetics
- Absorption
- Intravenous only.
- Elimination
- By the kidney, unchanged; adjusted in kidney failure.
- Half-life
- Short, 41 to 59 minutes.
Indications
- Intra-abdominal infections such as peritonitis and abscesses due to gram-negatives and anaerobes. Peritonitis →
- Gynaecological infections, including pelvic inflammatory disease. Pelvic inflammatory disease →
- Mixed anaerobic infections such as diverticulitis. Diverticular disease and diverticulitis →
- Prophylaxis in gastrointestinal surgery, hysterectomy and caesarean section.
Adverse effects
Common
- Thrombophlebitis at the infusion site
- Rash, eosinophilia
- Diarrhoea
Contraindications
- Hypersensitivity to cefoxitin or other cephalosporins
Key interactions
- Aminoglycosides
- More kidney toxicity; kidney function is monitored.
- Probenecid
- Reduces tubular secretion: higher and longer-lasting β-lactam levels.
- Creatinine measured by the Jaffé method
- High cefoxitin levels give falsely raised creatinine; do not draw the sample right after a dose.
What is monitored
- Kidney function (with an unaffected creatinine method)
- Infusion site
Administration and safety
- Intravenous, by slow injection or infusion.
- For creatinine, time the sample against the dose (false increases).
- Do not confuse cefoxitin with cefotaxime or ceftriaxone.
Nursing care
- Before the first dose: ask about allergy to penicillins, cephalosporins and other β-lactams, and what the reaction was.
- Rotate and watch the infusion site for thrombophlebitis.
- Watch urine output and creatinine, more so with aminoglycosides.
- Teach the patient to report watery or bloody diarrhoea, even weeks after the course ends.
Pregnancy and breastfeeding
Animal studies showed no fetal harm and there are no controlled studies in pregnant women; used if clearly needed.
Test yourself
Think of the answer, then tap the question to see it.
Which important anaerobe does cefoxitin cover and cefuroxime does not?
Bacteroides fragilis; that is why cefoxitin is used for mixed abdominal and pelvic infections.
Why can cefoxitin distort a creatinine result?
At high concentrations it interferes with the Jaffé method and gives false increases.
In which infections is cefoxitin used because of its spectrum?
Mixed aerobic–anaerobic infections such as intra-abdominal and pelvic ones, and prophylaxis for gastrointestinal and gynaecological surgery.
Related drugs
Related conditions
← Back to the class: Beta-lactams
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Cefoxitin Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - CEFOXITIN injection, powder, for solution (DailyMed (U.S. National Library of Medicine), 2026); RCSB PDB - 3MZE: Structure of penicillin-binding protein 5 from E.coli: cefoxitin acyl-enzyme complex (RCSB Protein Data Bank, 2026); Farmacología básica y clínica (Katzung), cap. 43 (McGraw Hill, 2025).
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Representative model, for educational purposes only.