Plasma and Tissue Concentration of Cefazolin in Preoperative Prophylaxis in Patients Undergoing Bariatric Surgery

November 19, 2025 updated by: François Julien, Laval University
This study investigates whether current cefazolin dosing guidelines for obese patients-2 g IV for those <120 kg and 3 g IV for those ≥120 kg-achieve adequate plasma and tissue concentrations (≥8 mg/L) for effective surgical prophylaxis. While several retrospective and prospective studies suggest that a 2 g dose may be sufficient regardless of weight, findings are inconsistent and often rely solely on plasma concentrations. Given that tissue concentration at the site of action is a more relevant pharmacokinetic marker, the study emphasizes the need to measure cefazolin levels in adipose tissue. Previous research using microdialysis has shown reduced tissue distribution in obese patients, potentially warranting higher doses. The study also highlights variability in defining the minimum inhibitory concentration (MIC) required for prophylaxis, noting that 8 mg/L is often considered the threshold for Enterobacteriaceae. Ultimately, the study aims to clarify whether current dosing achieves effective antibiotic levels across different weight categories, with a focus on tissue concentrations.

Study Overview

Status

Active, not recruiting

Conditions

Study Type

Observational

Enrollment (Actual)

70

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Canada
    • Quebec
      • Québec, Quebec, Canada, G1V 4G5
        • Institut universitaire de cardiologie et de pneumologie de Québec - Université Laval

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

All adults undergoing bariatric surgery.

Description

Inclusion Criteria:

  • Have a BMI ≥ 35 kg/m²
  • Undergo bariatric surgery (sleeve gastrectomy) via laparoscopy

Exclusion Criteria:

  • Under 18 years of age
  • Weight over 180 kg
  • Penicillin allergy
  • Pregnant or breastfeeding women
  • Chronic kidney disease (eGFR < 60 ml/min according to the Cockcroft-Gault equation)
  • Liver cirrhosis
  • Intraoperative blood loss ≥ 1 liter

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Clindamycin group/control
A control group of 10 patients undergoing sleeve gastrectomy at the Quebec Heart and Lung Institute, who have not been exposed to cefazolin due to penicillin allergy, will be recruited to validate the analytical method. During surgery, biopsies of adipose and dermal tissue and blood samples will be collected. No other antibiotic or medications will be administered to these patients.
Ancef group
Sixty patients will be recruited for the study, with 20 patients assigned to each weight category. Recruitment will take place during the preoperative consultation at the bariatric surgery clinic. All patients expressing interest will be included, provided they do not meet any exclusion criteria (convenience sampling). During surgery, biopsies of adipose and dermal tissue and blood samples, will be collected. No additional antibiotics or medications will be administered to these patients.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Area Under the Concentration-Time Curve (AUC) of Cefazolin in Plasma, Adipose Tissue, and Dermal Tissue
Time Frame: During surgery

AUC of cefazolin will be measured in plasma, adipose tissue, and dermal tissue at 0 minutes, 30 minutes, and at the end of surgery following administration according to current dosing guidelines.

Unit of Measure:

mg·min/L
During surgery

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Proportion of Patients Achieving Cefazolin Tissue Concentrations ≥ 8 mg/L
Time Frame: During surgery

Proportion of patients with adipose and dermal tissue concentrations of cefazolin ≥ 8 mg/L at any time point (0 min, 30 min, end of surgery), based on the MIC for Enterobacteriaceae.

Unit of Measure:

Percentage of patients (%)
During surgery
Proportion of Patients Achieving Cefazolin Plasma Concentrations ≥ 2 mg/L
Time Frame: During surgery

Proportion of patients with plasma concentrations of cefazolin ≥ 2 mg/L at each time point (0 min, 30 min, end of surgery), based on the MIC for methicillin-sensitive Staphylococcus aureus (MSSA).

Unit of Measure:

Percentage of patients (%)
During surgery
Comparison of Cefazolin Concentrations Across Weight Categories
Time Frame: During surgery

Comparison of plasma and tissue concentrations of cefazolin across weight categories (<120 kg, 120-149 kg, ≥150 kg) to identify potential underexposure in higher weight groups.

Unit of Measure:

Mean concentration (mg/L)
During surgery
Tissue-to-Plasma Concentration Ratio of Cefazolin
Time Frame: During surgery

Ratio of cefazolin concentration in tissue to plasma at each time point to assess distribution efficiency.

Unit of Measure:

Ratio (unitless)
During surgery
Time Above MIC (T>MIC) for Cefazolin in Plasma and Tissue
Time Frame: During surgery

Duration (in minutes) that cefazolin concentrations remain above MIC in plasma and tissue compartments, if additional time points are available.

Unit of Measure:

Minutes
During surgery

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
Screening and Eligibility Verification Through Demographic and Clinical Data
Time Frame: Preoperative period

Participants will be evaluated during preoperative consultation by a bariatric surgeon. If eligible, informed consent will be obtained. Demographic and clinical data will be collected to confirm inclusion criteria:

  • Height (cm)
  • Weight at recruitment (kg)
  • BMI at recruitment (kg/m²)
  • Allergy status to penicillin

Blood samples will confirm:

  • Absence of liver cirrhosis
  • Absence of chronic kidney disease (eGFR < 60 mL/min based on Cockcroft-Gault equation)
Preoperative period
Demographic Data Collected Before Surgery for Eligibility Assessment
Time Frame: preoperative period

Prior to the start of surgery, demographic data will be collected to confirm participant eligibility according to inclusion criteria and establish baseline characteristics.

Data collected:

  • Age (years)
  • Weight at admission (kg); will be used to determine the appropriate prophylactic dose of cefazolin.
  • Body Mass Index (BMI) at admission (kg/m²)
preoperative period

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Laval University

Collaborators

Fondation IUCPQ

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

April 11, 2019

Primary Completion (Actual)

February 16, 2022

Study Completion (Estimated)

February 1, 2026

Study Registration Dates

First Submitted

November 13, 2025

First Submitted That Met QC Criteria

November 19, 2025

First Posted (Actual)

November 28, 2025

Study Record Updates

Last Update Posted (Actual)

November 28, 2025

Last Update Submitted That Met QC Criteria

November 19, 2025

Last Verified

November 1, 2025

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • CER 21626, 2019-3053

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Not applicable for this study

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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