Cefoxitin
Cefoxitin sodium
Also known as: Mefoxin · Mefoxitin · Cefociclin · Cefoxin · MK-306 · L-620-388 · cefoxitinum · cefoxitina · cefoxitine
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Mixed infections (e.g., aspiration pneumonia, bowel perforation) | 30 mg/kg SC q8h; 30 mg/kg IV q4-6h | SC/IV | q8h or q4-6h | — | 🌎 NA |
| Sepsis | 30 mg/kg IV q5h | IV | q5h | — | 🌎 NA |
| Soft tissue infections | 30 mg/kg SC q8h or 30 mg/kg IV q5h | SC/IV | q8h or q5h | — | 🌎 NA |
| Bacteremia | 15-30 mg/kg IV, IM SC q6-8h | IV/IM/SC | q6-8h | — | 🌎 NA |
| Orthopedic infections | 22 mg/kg IV, IM q6-8h | IV/IM | q6-8h | Use as long as necessary to control initial infection, then switch to oral drugs | 🌎 NA |
| Susceptible infections | 30 mg/kg SC q8h | SC | q8h | — | 🌎 NA |
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Systemic infections | 25-30 mg/kg IV or IM q8h | IV/IM | q8h | Use as long as necessary to control initial infection, then switch to oral drugs | 🌎 NA |
| Sepsis | 30 mg/kg IV q5h | IV | q5h | — | 🌎 NA |
| Susceptible infections | 30 mg/kg IV q8h | IV | q8h | — | 🌎 NA |
| Non-tuberculosis mycobacteria (NTM) - second line treatment | 30-40 mg/kg IV, IM or SC q6-8h | IV/IM/SC | q6-8h | — | 🌎 NA |
- Non-tuberculosis mycobacteria (NTM) - second line treatment: Causes pain on injection with IM or SC
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible infections (Foals) | 20 mg/kg IV q4-6h | IV | q4-6h | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
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 of action
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 → inhibits the transpeptidation enzyme responsible for cross-linking peptidoglycan strands.
- Lack of cross-linking → weakens the bacterial cell wall → 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.
Safety & warnings
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)
Precautions
Important Precautions
- Renal Impairment: Patients in renal failure may require dosage adjustments as the drug is primarily eliminated via the kidneys.
- Cross-Reactivity: Cross-hypersensitivity with penicillins can occur (estimated 1-15% in humans; unknown in veterinary species).
- Administration: Causes pain on IM injection. When giving IV, administer slowly over 3-5 minutes or more to minimize adverse reactions.
- Laboratory Interference: May cause false-positive urine glucose tests (cupric sulfate method) and falsely elevated serum/urine creatinine values (Jaffe reaction).
Drug interactions
Potential for additive nephrotoxicity. While in vitro synergy exists against certain bacteria, they should not be mixed in the same syringe or fluid bag.
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
Pharmacokinetics
Half-life
Absorption
Not appreciably absorbed after oral administration; must be given parenterally to achieve therapeutic serum levels.
Distribution
Widely distributed. In horses, Vd at steady state is 110 mL/kg. In calves, Vd is 318 mL/kg and it is ~50% protein bound. Crosses the placenta and distributes into milk in low concentrations.
Metabolism
Minimal. In humans, approximately 2% of a dose is metabolized to inactive descarbamylcefoxitin.
Elimination
Primarily excreted unchanged by the kidneys into the urine via both tubular secretion and glomerular filtration. Elimination is significantly prolonged in severe renal failure.
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.
Available products
Formulations
- Powder for injection
Human-labeled
- Cefoxitin Sodium Powder for Injection: 1 g, 2 g, & 10 g in vials & infusion bottles
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store powder for injection < 30°C; do not expose to > 50°C. Frozen solutions should be stored <= -20°C. After reconstitution, stable for 24 hours at room temperature and 48 hours to 1 week if refrigerated. If immediately frozen after reconstitution, stable up to 30 weeks at -20°C. Darkening of the powder/solution does not affect potency.
Client information
Cefoxitin is a potent, injectable antibiotic typically administered by veterinary professionals in a clinic or hospital setting to treat severe or complex infections.
- Administration: Because it is given by injection, you will likely not be administering this at home. If your pet is receiving injections under the skin (SC) or in the muscle (IM), they may experience some temporary pain or swelling at the injection site.
- Side Effects: While generally very safe, some pets may develop mild diarrhea or stomach upset.
- Allergies: Inform your veterinarian immediately if your pet has ever had an allergic reaction to penicillin or other antibiotics, or if you notice signs of an allergic reaction (facial swelling, hives, difficulty breathing) during treatment.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.