Cefazolin dosing for surgical prophylaxis in morbidly obese patients.
BACKGROUND
Cefazolin is used commonly to prevent surgical site infection (SSI) after operations on patients with morbid obesity (MO), but specific dosing guidelines are lacking. We hypothesized that cefazolin 2 g given by intravenous (IV) push over 5 min (IVP) or infusion over 30 min (INF) would suffice for SSI prophylaxis in MO (body mass index [BMI] 40-50 kg/m(2)), and cefazolin 3 g would be sufficient in patients with super-morbid obesity (SMO) (BMI >50 kg/m(2)).


METHODS
Twenty-five patients undergoing elective surgical procedures were given a single dose of cefazolin: Ten with MO received 2 g via IVP (MO2-IVP), five with MO received 2 g via 30-min infusion (MO2-INF), five with SMO received 2 g via infusion (SMO2-INF), and five with SMO received 3 g via infusion (SMO3-INF). Serum cefazolin concentrations were measured 5, 30, 120, and 360 min after initiation of the dose. The half-life of the drug was calculated for each patient, as was the time the concentration was above the minimum inhibitory free concentration (fT>MIC) using 8 mcg/mL as the breakpoint. The protective duration of each cefazolin dose was assessed using the pharmacodynamic target for fT>MIC of 70%.


RESULTS
The mean cefazolin concentrations after 30 min were similar in all groups; the mean concentrations at 120 and 360 min were 67.1-84.8 mcg/mL and 22.9-40.8 mcg/mL, respectively. The half-life ranged from 2.3 to 3.6 h and was unaffected by administration method. The protective duration was 5.1 h for MO2-IVP, 4.8 h for MO2-INF, 5.8 h for SMO2-INF, and 6.8 h for SMO3-INF.


CONCLUSIONS
A single 2-g dose of cefazolin appears to provide antibiotic exposures sufficient for most common general surgical procedures of <5-h duration, regardless of BMI.
Department of Surgery, Weill Cornell Medical College, New York, New York, USA. vah9004@nyp.org
Vanessa P
VP
Ho
David P
DP
Nicolau
Gregory F
GF
Dakin
Alfons
A
Pomp
Barrie S
BS
Rich
Christopher W
CW
Towe
Philip S
PS
Barie
D000328:Adult; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D019072:Antibiotic Prophylaxis / Q000379:methods*; D015992:Body Mass Index; D002437:Cefazolin / Q000008:administration & dosage* / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D017558:Elective Surgical Procedures; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000601:surgery*; D013530:Surgical Wound Infection / Q000517:prevention & control*
D000900:Anti-Bacterial Agents; D002437:Cefazolin