Cephamycin (2nd-gen-like, anaerobic cover) Pregnancy: Animal studies have not shown evidence of a teratogenic effect and a large amount of clinical data in pregnant women indicate no malformative nor feto/neonatal toxicity; nevertheless epidemiological studies would be required to verify the absence of risk, so it should only be used during pregnancy if clinically needed. Breast-feeding: cefoxitin is excreted in human milk and breast-feeding should be discontinued during administration to prevent allergic reactions in the infant.

Cefoxitin

Brand names: Mefoxin

Cefoxitin is a cephamycin (cephalosporin-type) parenteral antibacterial with useful activity against anaerobes, used for mixed aerobic-anaerobic infections such as intra-abdominal and gynaecological infections.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 2 g

Route: Intravenous — by slow intravenous injection over 3 to 5 minutes, or by continuous intravenous infusion

Frequency: Every 4 to 6 hours

Max: 12 g per day

UK SPC (Renoxitin 1 g powder for solution for injection or infusion), adults and adolescents: 2 g every 4 to 6 hours to a maximum of 12 g/day. IMPORTANT CAVEAT FROM THE SPC ITSELF: 'There are very limited clinical safety and efficacy data supporting the dose of cefoxitin. Therapeutic guidelines should be adhered to.' The stated regimen is what 'may be appropriate' on the basis of those very limited clinical data plus supporting pharmacokinetic/pharmacodynamic data. PAEDIATRIC: the UK SPC states there are insufficient data to recommend a posology in children aged up to 11 years — no paediatric dose is given, so none is published here (for reference, the US label in the same bundle quotes 80 to 160 mg/kg/day divided into four to six equal doses in children 3 months and older, total not to exceed 12 g/day, with no recommendation from birth to 3 months; that is US labelling, is not the UK position, and must be checked against a children's formulary rather than used from this draft). The UK SPC gives no surgical prophylaxis regimen; the US label in the bundle describes prophylaxis (2 g IV just before surgery then 2 g every 6 hours for no more than 24 hours) — verify separately before publishing.

Dose adjustments

Renal

There are extremely little data on cefoxitin in renal impairment and great caution is advised. In adults an initial loading dose of 2 g may be given, then maintenance: CrCl 50 to 30 mL/min — 2 g every 8 to 12 hours; CrCl 29 to 10 mL/min — 2 g every 12 to 24 hours. In patients on haemodialysis the 2 g loading dose should be given after each haemodialysis, with maintenance as in the table.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance, to any other cephalosporin antibiotic or to any of the excipients
History of severe hypersensitivity (e.g. anaphylactic reaction) to any other type of beta-lactam antibacterial agent (penicillins, monobactams and carbapenems)

Side effects

Local reactions — local thrombophlebitis after intravenous administration; injection site reaction; pyrexia (frequency not known)
Gastrointestinal — nausea, vomiting, diarrhoea, pseudomembranous colitis (frequency not known)
Hypersensitivity — rash, urticaria, pruritus, angioedema, toxic epidermal necrolysis, anaphylactic reaction (frequency not known)
Haematological — eosinophilia, leukopenia, neutropenia (agranulocytosis), anaemia including haemolytic anaemia, thrombocytopenia, bone marrow failure (frequency not known)
Encephalopathy (confusion, disorders of consciousness, seizure, abnormal movements), particularly with overdose or reduced renal function; also raised transaminases, LDH and alkaline phosphatase, interstitial nephritis, raised creatinine/BUN and severe renal impairment

Interactions

Aminoglycosides and other potentially nephrotoxic antibiotics — monitor renal function during concomitant treatment; increased nephrotoxicity has been reported with cephalosporins plus aminoglycosides
Furosemide and etacrynic acid diuretics — monitor renal function during concomitant treatment
Laboratory tests — false-positive Coombs test; false-positive glycosuria with reduction substances (no interaction with enzymatic methods); interference with the Jaffe creatinine method

Clinical monograph

How it works

It is a beta-lactam that inhibits bacterial cell-wall synthesis by binding penicillin-binding proteins, producing a bactericidal effect, and is relatively stable to some bacterial beta-lactamases.

Prescribing in practice

Avoid in patients with a history of immediate hypersensitivity to penicillins or other beta-lactams because of the risk of cross-reactivity.
Its anaerobic cover makes it useful for mixed infections, but local resistance patterns and microbiology advice should guide use.
Dose adjustment is required in significant renal impairment, in line with the SPC.

Monitoring

Monitor renal function and clinical response, especially during prolonged therapy or in renal impairment.

Counselling the patient

This antibiotic is given by injection or infusion under clinical supervision.
Report any rash, swelling, breathing difficulty, or severe or persistent diarrhoea.

Evidence & guidelines

Its role in surgical and intra-abdominal infection is established in standard microbiology and prescribing references rather than a single landmark trial.

Reference: BSAC; UKHSA; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Pathways