MEFOXIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MEFOXIN (MEFOXIN).
Cefoxitin is a cephamycin antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), thereby inhibiting peptidoglycan cross-linking.
| Metabolism | Primarily hepatic metabolism; minimal metabolism via deacetylation. |
| Excretion | Primarily renal (85% unchanged) via glomerular filtration and tubular secretion; small biliary/fecal (<5%) |
| Half-life | Terminal elimination half-life 0.7-1.1 hours in normal renal function; prolonged to 5-9 hours in severe renal impairment (CrCl <10 mL/min) |
| Protein binding | 65-80% bound to serum albumin |
| Volume of Distribution | 0.12-0.15 L/kg; approximates extracellular fluid volume |
| Bioavailability | IM: ~85% |
| Onset of Action | Intravenous: immediate; intramuscular: 15-30 minutes |
| Duration of Action | 6-8 hours for susceptible organisms; prolonged in renal impairment |
| Molecular Weight | 427.45 |
1-2 g IV every 6-8 hours; usual dose 1 g IV every 6 hours for uncomplicated infections, 2 g IV every 6-8 hours for severe infections. Maximum 12 g/day.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 30-50 mL/min: 1-2 g every 8 hours. CrCl 10-29 mL/min: 1-2 g every 12 hours. CrCl <10 mL/min: 1-2 g every 24-48 hours. For continuous ambulatory peritoneal dialysis (CAPD): 1 g every 24 hours. For hemodialysis: 1-2 g after each dialysis session. |
| Liver impairment | No specific Child-Pugh based modifications available; caution in severe hepatic impairment due to potential toxicity, but no standard dose adjustment recommended. |
| Pediatric use | Infants and children >3 months: 80-160 mg/kg/day IV divided every 6-8 hours. Maximum 12 g/day. Neonates: weight-based dosing per gestational age: <2 weeks: 100 mg/kg/day IV divided every 12 hours; >2 weeks: 100-150 mg/kg/day IV divided every 8-12 hours. |
| Geriatric use | No specific dose adjustment based solely on age; use weight and renal function to determine dose. Monitor renal function closely. |
| 1st trimester | Crosses placenta; limited human data; avoid unless essential. |
| 2nd trimester | Use with caution; cefoxitin is generally considered low risk. |
| 3rd trimester | Use with caution; theoretical risk of kernicterus in neonates. |
Clinical note
Comprehensive clinical and safety monograph for MEFOXIN (MEFOXIN).
| Placental transfer | Crosses placenta; achieves therapeutic levels in fetal tissues. |
| Breastfeeding | Excreted into breast milk in low amounts; considered compatible with breastfeeding. |
| Lactation Rating | L2 |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to cefoxitin or other cephalosporinsHistory of immediate hypersensitivity reaction to penicillins
| Precautions | Hypersensitivity reactions including anaphylaxis, Clostridioides difficile-associated diarrhea (CDAD), Seizures at high doses in patients with renal impairment, Prolonged bleeding time, Overgrowth of non-susceptible organisms |
| Food/Dietary | No specific food interactions. However, avoid alcohol (including in foods/medicines) due to risk of disulfiram-like reaction (flushing, tachycardia, nausea, vomiting). |
| Clinical Pearls |
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| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; insufficient human data. Use only if clearly needed. |
| Fetal Monitoring | No specific fetal monitoring required. Observe for maternal adverse effects (hypersensitivity, diarrhea). |
| Fertility Effects | No known adverse effects on human fertility. |
| MEFOXIN (cefoxitin) is a cephamycin antibiotic with activity against anaerobes, including Bacteroides fragilis. It is often used for surgical prophylaxis, particularly in colorectal and gynecologic procedures. Note that it has no activity against enterococci or Pseudomonas aeruginosa. Dose adjustment required in renal impairment (CrCl < 30 mL/min). May cause false positive on direct Coombs test. |
| Patient Advice | Take exactly as prescribed; finish the full course even if you feel better. · Report any signs of allergic reaction (rash, itching, swelling, difficulty breathing) immediately. · May cause diarrhea; contact your doctor if it becomes severe or bloody. · Avoid alcohol during treatment and for 48 hours after last dose (disulfiram-like reaction possible). · Inform your doctor if you have kidney disease, colitis, or are allergic to cephalosporins or penicillins. |