Cefazolin Dosing for Surgical Prophylaxis in a 130kg Patient
For a 130kg patient undergoing surgery, administer cefazolin 3 grams intravenously within 60 minutes before surgical incision.
Weight-Based Dosing Rationale
The standard surgical prophylaxis dose of cefazolin is 1-2 grams for normal-weight patients 1. However, patients weighing over 120kg require dose escalation to 3 grams to achieve adequate tissue concentrations 2.
Specific Dosing by Weight Category:
- Patients 50-100kg: 2 grams cefazolin 1
- Patients 100-120kg: 2 grams cefazolin 1
- Patients >120kg (including your 130kg patient): 3 grams cefazolin 2
The pharmacokinetic data demonstrates that in overweight and obese patients, a 2-gram dose achieves target tissue concentrations above the MIC (minimum inhibitory concentration of 2 μg/mL) in 92.4% of patients at 1.5 hours, while a 3-gram dose achieves this in 94.7% of patients 2. For a 130kg patient, the 3-gram dose provides the highest probability of maintaining adequate adipose tissue concentrations throughout the surgical procedure 2.
Administration Timing and Technique
- Administer within 60 minutes prior to surgical incision to ensure adequate serum and tissue concentrations at the time of initial incision 3, 4
- Give as intravenous bolus over 3-5 minutes 1
- If the surgical incision is delayed beyond 1 hour after administration, redose with another full dose 4
Intraoperative Redosing Requirements
Redose with 1-2 grams cefazolin if the surgical procedure exceeds 4 hours (approximately 2-3 half-lives of cefazolin) 4, 1. For lengthy procedures:
- Administer additional doses every 4 hours during surgery 1
- This maintains tissue concentrations above the MIC throughout the entire procedure 4
Postoperative Duration
Discontinue cefazolin prophylaxis within 24 hours postoperatively 1. The FDA label recommends 500mg-1g every 6-8 hours for 24 hours postoperatively for routine cases 1. However, extending prophylaxis beyond 24 hours provides no additional benefit and increases antimicrobial resistance risk 3, 4.
For high-risk procedures (open-heart surgery, prosthetic arthroplasty), prophylaxis may be continued for 3-5 days, though this is not standard practice 1.
Common Pitfalls to Avoid
- Do not use the standard 1-2 gram dose in obese patients - this results in subtherapeutic tissue concentrations and increased surgical site infection risk 2
- Do not forget to redose if incision is delayed >1 hour after initial administration 4
- Do not continue prophylaxis beyond 24 hours for routine procedures - this promotes resistance without improving outcomes 3
- Do not administer too early - giving cefazolin more than 60 minutes before incision results in declining tissue levels during the critical contamination period 3, 4