Cefoxitin
Cefoxitin is a **second-generation parenteral cephalosporin** (technically classified as a cephamycin) used in veterinary medicine for severe or mixed bacterial infections. Key pharmacological highlights include: * **Anaerobic Efficacy**: Unlike many other early-generation cephalosporins, cefoxitin is highly effective against **anaerobic bacteria**, including *Bacteroides fragilis*. * **Gram-Negative Spectrum**: It exhibits good activity against many strains of *E. coli*, *Klebsiella*, and *Proteus* that may be resistant to first-generation agents. * **Gram-Positive Spectrum**: It retains activity against gram-positive cocci, though slightly less potent on a per-weight basis compared to first-generation cephalosporins. > **Clinical Pearl**: Because of its strong anaerobic spectrum, cefoxitin is frequently chosen for mixed infections such as aspiration pneumonia, bowel perforations, and severe soft tissue infections or sepsis.
Mechanism: Cefoxitin is a **bactericidal** antibiotic that works by inhibiting bacterial cell wall synthesis. * It covalently binds to specific **Penicillin-Binding Proteins (PBPs)** located inside the bacterial cell wall. * Binding to PBPs โ **inhibits the transpeptidation enzyme** responsible for cross-linking peptidoglycan strands. * Lack of cross-linking โ weakens the bacterial cell wall โ leads to osmotic instability, cell lysis, and bacterial death. * As a cephamycin, cefoxitin is highly resistant to degradation by many **beta-lactamases**, particularly those produced by *Bacteroides* species.
Dosing by species
- Systemic infections ยท 25-30 mg/kg IV or IM q8h ยท IV/IM ยท q8h ยท Use as long as necessary to control initial infection, then switch to oral drugs
- Sepsis ยท 30 mg/kg IV q5h ยท IV ยท q5h
- Susceptible infections ยท 30 mg/kg IV q8h ยท IV ยท q8h
- Non-tuberculosis mycobacteria (NTM) - second line treatment ยท 30-40 mg/kg IV, IM or SC q6-8h ยท IV/IM/SC ยท q6-8h ยท Causes pain on injection with IM or SC
- Susceptible infections (Foals) ยท 20 mg/kg IV q4-6h ยท IV ยท q4-6h
- Mixed infections (e.g., aspiration pneumonia, bowel perforation) ยท 30 mg/kg SC q8h; 30 mg/kg IV q4-6h ยท SC/IV ยท q8h or q4-6h
- Sepsis ยท 30 mg/kg IV q5h ยท IV ยท q5h
- Soft tissue infections ยท 30 mg/kg SC q8h or 30 mg/kg IV q5h ยท SC/IV ยท q8h or q5h
- Bacteremia ยท 15-30 mg/kg IV, IM SC q6-8h ยท IV/IM/SC ยท q6-8h
- Orthopedic infections ยท 22 mg/kg IV, IM q6-8h ยท IV/IM ยท q6-8h ยท Use as long as necessary to control initial infection, then switch to oral drugs
Routes of administration
Contraindications
- Patients with a history of hypersensitivity to cephalosporins
- Use with extreme caution in patients documented to be hypersensitive to other beta-lactams (penicillins, carbapenems)
Adverse effects
- Hypersensitivity reactions (rashes, fever, eosinophilia, lymphadenopathy, anaphylaxis)
- Pain at the injection site (IM)
- Sterile abscesses or local tissue reactions
- Thrombophlebitis (IV administration)
- Antibiotic-associated diarrhea or altered gut flora
- Superinfections
- Nephrotoxicity (rare at clinical doses)
- Neurotoxicity, neutropenia, thrombocytopenia, hepatitis (associated with high doses or prolonged use)
Drug interactions
- Aminoglycosides / Nephrotoxic Drugs ยท Potential for additive nephrotoxicity. While in vitro synergy exists against certain bacteria, they should not be mixed in the same syringe or fluid bag.
- Probenecid ยท Competitively blocks the tubular secretion of cefoxitin, thereby increasing serum levels and prolonging elimination half-lives.
Monitoring
- Clinical efficacy (resolution of infection signs)
- Renal function (BUN, creatinine, urinalysis) in patients with diminished renal capacity
Overdose
Acute oral cephalosporin overdoses are unlikely to cause significant problems other than **gastrointestinal distress**. Massive parenteral overdoses or prolonged accumulation (especially in renal failure) may lead to: * Neurotoxicity (seizures) * Neutropenia or thrombocytopenia * Hepatitis * Nephrotoxicity (tubular necrosis) Treatment is supportive and symptomatic.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.