What is the recommended dose of Mefoxin (cefoxitin) for a 108kg male with acute cholecystitis?

Mefoxin (Cefoxitin) Dosing for a 108kg Male with Acute Cholecystitis

For a 108kg male with acute cholecystitis, the recommended dose of Mefoxin (cefoxitin) is 200 mg/kg/day in three divided doses, which equals 21.6g/day (7.2g every 8 hours), but this must be capped at the maximum daily dose of 12g/day (4g every 8 hours) administered via intravenous infusion. 1, 2

Dosing Calculation and Administration

1. Weight-based calculation:

   • Standard adult dose: 200 mg/kg/day 1
   • For 108kg patient: 200 mg/kg × 108kg = 21,600 mg/day (21.6g/day)
   • However, this exceeds the maximum daily dose

2. Final dosing recommendation:

   • Maximum daily dose: 12g/day 1, 2
   • Administration: 4g every 8 hours via intravenous infusion

3. Administration method:

   • Doses over 2g should be given by intravenous infusion diluted in sodium chloride 0.9% or glucose 5% 1
   • Complete the entire preparation process within 4 hours of initial entry 2

Duration of Therapy

• For acute cholecystitis, antibiotic therapy should typically be continued for 3-5 days 3
• Discontinue antibiotics when:
  • Patient is afebrile for 24 hours
  • White blood cell count normalizes
  • No signs of ongoing infection are present 3

Monitoring Recommendations

1. Laboratory monitoring:

   • Routine toxicity monitoring with FBC, U&Es, LFTs throughout treatment 1
   • Monitor for clinical improvement (decreasing fever, abdominal pain, normalizing WBC) 3

2. Renal function considerations:

   • For patients with renal impairment, dose adjustment is necessary 2
   • For severe renal impairment (creatinine clearance 9-10 mL/min), reduce to 0.5-1g every 12-24 hours 2

Potential Adverse Effects

1. Common adverse effects:

   • Hypersensitivity reactions
   • Maculopapular rash, urticaria
   • Transient increases in liver enzymes
   • Injection site reactions (thrombophlebitis or phlebitis) 1

2. Serious adverse effects to monitor:

   • Stevens-Johnson syndrome
   • Hematological effects (leucopenia, thrombocytopenia)
   • Hepatic dysfunction
   • Pseudomembranous colitis
   • Seizures (rare)
   • Acute renal failure (rare) 1

Important Drug Interactions

• Aminoglycosides: Increased risk of nephrotoxicity
• Anticoagulants: Increased INR with warfarin
• Furosemide: Increased risk of nephrotoxicity
• Probenecid: Reduced renal excretion of cefoxitin 1

Clinical Considerations for Acute Cholecystitis

• Cefoxitin has shown efficacy in treating biliary tract infections with favorable response rates of approximately 71-80% 4
• While cefoxitin is effective, current guidelines for acute cholecystitis also suggest other options like cefazolin, cefuroxime, or ceftriaxone for mild-to-moderate community-acquired cases 3
• For severe or healthcare-associated cases, broader coverage may be needed 3

Caveats and Pitfalls

1. Do not exceed the maximum daily dose of 12g, regardless of weight-based calculations 1, 2
2. Monitor for interference with creatinine measurements, as cefoxitin can produce falsely high values in common assays 1
3. Be aware of potential for pseudomembranous colitis, which can occur during or after antibiotic treatment 1
4. Always obtain bile cultures when possible to guide targeted therapy 5
5. Consider surgical intervention timing, as early laparoscopic cholecystectomy (within 24-72 hours) is the definitive treatment of choice for acute cholecystitis 3

Cefoxitin remains an effective antibiotic for biliary tract infections, but dosing must adhere to maximum limits regardless of patient weight, and appropriate monitoring for adverse effects should be implemented throughout the treatment course.