Adequacy of Perioperative Cefazolin for Surgery Antibiotic Prophylaxis in Obese Patients

University of Colorado Denver (CU Denver) logo

University of Colorado Denver (CU Denver)

Status and phase

Phase 4




Drug: Weight Based Group
Drug: Standard Dose Group

Study type


Funder types




Details and patient eligibility


The population continues to increase in weight. Currently there are no guidelines in the dosing of cefazolin for the obese population. Standard dosing of cefazolin 2 grams for patients <120 kg and 3 grams for patients >120 kg is used as the dose for surgical prophylaxis. This makes no provisions for weight based dosing. There has been some recent data which states this might not be enough for the obese patients. The primary objective of this study is to determine if weight based dosing (30 mg/kg) of cefazolin as surgical prophylaxis for patients undergoing elective gastric bypass/laparoscopic Roux-en-y gastric bypass provides appropriate serum concentrations for a larger percentage of time than the current method of giving the standard 2 or 3 gram doses of cefazolin peri-operatively. The concentration of cefazolin in tissue will also be measured to help assess this question.

Full description

The hypothesis of this study is that customary doses of antibiotics, when administered for perioperative surgical prophylaxis, are insufficient to achieve adequate antibiotic concentrations in blood and tissues of morbidly obese patients (defined as a BMI greater than 40 kg/m2) and that these patients are therefore placed at high risk of surgical wound infections and poor clinical outcomes. Cefazolin is a first-generation cephalosporin commonly used for perioperative surgical prophylaxis in colorectal, abdominal, bariatric, gynecologic and obstetric, or orthopedic total joint arthroplasty surgical procedures. Previous cefazolin pharmacokinetic (PK) analysis in obese patients led to conflicting results and recommendations. It is not clearly know to what extent the pharmacokinetics of cefazolin in morbidly obese patients differ from those of non-obese patients. Specific dosing guidelines are then lacking. The main objective of this study is to assess the pharmacokinetics of cefazolin in morbidly obese after administrations of a standard recommended 2-3 g dose or a weight-base 30-mg/kg dose




18 to 75 years old


No Healthy Volunteers

Inclusion criteria

  • BMI greater than 40
  • No known history of allergy to cephalosporins
  • Scheduled for elective gastric bypass or laparoscopic Roux-en-y gastric bypass procedures
  • Able to read and understand English

Exclusion criteria

  • Patients <18 years of age or >89 Years of age
  • Pregnant women, prisoners and decisionally challenged subjects will be excluded

Trial design

Primary purpose




Interventional model

Parallel Assignment


None (Open label)

0 participants in 2 patient groups

Control group
Active Comparator group
Standard dose group (2 g intravenous (IV) cefazolin dose for patients <120 kg, and 3 g IV cefazolin for patients >120 kg)
Drug: Standard Dose Group
Treatment group
Experimental group
Weight-based dose group (30 mg/kg cefazolin IV)
Drug: Weight Based Group

Trial contacts and locations



Data sourced from

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