Effect of body mass index on treatment of complicated intra-abdominal infections in hospitalized adults: comparison of ertapenem with piperacillin-tazobactam.
BACKGROUND
Complicated intra-abdominal infections (cIAI) are a common problem in surgical practice. The effect of body mass index (BMI) on the outcome is poorly understood. We compared the association of BMI and type of antibiotic therapy for cIAI described in a previously published trial of ertapenem vs. piperacillin-tazobactam (Namias N, Solomkin JS, Jensen EH, et al. Randomized, multicenter, double-blind study of efficacy, safety, and tolerability of intravenous ertapenem versus piperacillin/tazobactam in treatment of complicated intra-abdominal infections in hospitalized adults. Surg Infect 2007;8:15-28).


METHODS
A post-hoc analysis was performed using data obtained from the published study. The effect of BMI and type of antibiotic used for therapy were calculated for clinically favorable outcomes at early follow-up assessment (EFA).


RESULTS
The 231 patients who were microbiologically evaluable at EFA were stratified by BMI (<30 or ≥30 kg/m(2)). Twelve patients were excluded because of missing BMI data, leaving 219 patients for analysis. There were some differences in baseline characteristics between patients with a BMI <30 kg/m(2), including the source of intra-abdominal infection (more appendicitis in BMI <30 group; p=0.01) and gender (more men in the BMI <30 group; p=0.03). There was no difference in cure rates between the groups (82.9% for BMI <30 kg/m(2) vs. 74.5% for those with BMI ≥30 kg/m(2); 8% difference in proportions, 95% confidence interval [CI] -5%, 25%). There was an 80% favorable clinical response to ertapenem in the BMI <30 group compared with an 81% favorable rate in the BMI ≥30 group (-1% difference in proportions; 95% CI -22%, 19%). This compared with an 86% favorable response rate to piperacillin-tazobactam in the BMI <30 group vs. a 65% favorable clinical response rate in the BMI ≥30 group (21% difference in proportions; 95% CI -1%, 47%).


CONCLUSIONS
There was no difference in the cure rate of patients with cIAI in the BMI <30 and BMI ≥30 kg/m(2) groups. There were no statistically significant differences in the likelihood of response to an antibiotic regimen. However, there was a nominally 21% lower cure rate in the high BMI group receiving piperacillin-tazobactam (86% vs. 65%; 21% difference in proportions; 95% CI -1%, 47%), whereas there was only a 1% difference in the cure rate between BMI groups in the patients receiving ertapenem. This difference may be related to gender and etiology of infection. Although limited by the small number of high BMI patients and post-hoc methodology, these results merit consideration of the design of future prospective antibiotic trials to include stratification for BMI and consideration of the effect of BMI on pharmacokinetics and pharmacodynamics.
Division of General Surgery, St. Michael's Hospital, University of Toronto, Toronto, Canada.
Tanya L
TL
Zakrison
Darcy A
DA
Hille
Nicholas
N
Namias
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D015992:Body Mass Index; D000077727:Ertapenem; D005260:Female; D006801:Humans; D059413:Intraabdominal Infections / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D009767:Obesity, Morbid / Q000601:surgery; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000627:therapeutic use; D010878:Piperacillin / Q000627:therapeutic use; D000077725:Piperacillin, Tazobactam Drug Combination; D016032:Randomized Controlled Trials as Topic; D055815:Young Adult; D047090:beta-Lactams / Q000627:therapeutic use*
D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D000077725:Piperacillin, Tazobactam Drug Combination; D010397:Penicillanic Acid; D000077727:Ertapenem; D010878:Piperacillin