Cefazolin Dosing for Cesarean Section Based on Patient Weight
For cesarean section prophylaxis, patients weighing <120 kg should receive 2 g of cefazolin, while patients weighing ≥120 kg should receive 3 g, administered 30-60 minutes before skin incision. 1
Dosing Recommendations Based on Weight
The dosing of cefazolin for cesarean section prophylaxis should follow these weight-based guidelines:
- Patients <120 kg: 2 g IV cefazolin as a single dose
- Patients ≥120 kg: 3 g IV cefazolin as a single dose
Timing and Administration
- Administer cefazolin 30-60 minutes before skin incision (not after cord clamping) 1
- Single dose is generally sufficient 1
- Additional dose may be needed if:
- Procedure duration exceeds 4 hours (for 2 g dose)
- Procedure duration exceeds 2 hours (for 3 g dose)
- Significant blood loss occurs (>1.5 L) 1
Rationale for Weight-Based Dosing
The higher dose for patients ≥120 kg is recommended because:
- Obesity is a significant risk factor for surgical site infections after cesarean delivery 2, 3
- Adequate tissue concentrations are critical for preventing infection
- Pharmacokinetic studies show that standard dosing may not achieve adequate tissue concentrations in obese patients 2
Clinical Evidence Supporting Recommendations
Research has demonstrated that:
- In patients weighing ≥120 kg, a 3 g dose achieves higher tissue and blood concentrations than a 2 g dose 3
- Plasma and myometrial tissue concentrations are significantly higher with higher doses in obese patients 4
- Subcutaneous tissue concentrations at incision and closure sites are higher with increased dosing 4
Important Considerations
- Cefazolin should be administered before skin incision rather than after cord clamping to reduce the risk of surgical site infections 1
- Antibiotic prophylaxis alone cannot prevent surgical site infections; proper surgical technique and infection control practices are also essential 1
- For prolonged procedures, redosing may be necessary to maintain adequate tissue concentrations 3
Potential Pitfalls
- Timing errors: Administering cefazolin after cord clamping rather than before incision significantly reduces effectiveness
- Underdosing: Using standard 1 g dosing for all patients regardless of weight may lead to inadequate tissue concentrations in obese patients
- Failure to redose: Not providing additional doses during prolonged procedures can result in subtherapeutic levels
This weight-based dosing approach ensures optimal antibiotic concentrations at the surgical site to reduce the risk of postoperative infections, which directly impacts morbidity, mortality, and quality of life outcomes for patients undergoing cesarean delivery.