Risk of Neutropenia in Adults Treated with Piperacillin–Tazobactam or Cefazolin: A Retrospective Cohort Study

Background: Neutropenia is an adverse effect associated with the use of several antibiotics, including piperacillin–tazobactam (P/T). Previous findings have suggested that the risk of neutropenia in children is significantly higher with P/T than with ticarcillin–clavulanate. Objectives: To compare the risk of neutropenia associated with P/T and with cefazolin in an adult population and to describe the characteristics of neutropenia episodes observed. Methods: This descriptive retrospective study involved patients aged 18 years or older who received a minimum of 10 days of treatment with P/T or cefazolin between January 2009 and December 2013. Patients who experienced neutropenia (absolute neutrophil count < 1.5 × 109/L) were compared, using univariate and multivariate logistic regression models, between those who received P/T and those who received cefazolin. Results: A total of 207 patients were included (104 who received P/T and 103 who received cefazolin). Ten episodes of neutropenia were observed, 5 with each antibiotic (4.8% and 4.9%, respectively; odds ratio 0.99, 95% confidence interval 0.278–3.527). The mean cumulative dose of piperacillin was 290.4 g among patients who experienced neutropenia and 247.0 g among all patients treated with P/T, and the mean treatment duration was 24.0 days and 21.0 days, respectively. The average time before the onset of neutropenia was slightly longer with P/T than with cefazolin (22.0 versus 17.2 days, p = 0.38). Conclusions: Although these results require confirmation in a larger clinical trial (to lessen possible attribution bias), the risk of neutropenia appeared to be similar between P/T and cefazolin. RÉSUMÉ Contexte : La neutropénie est un effet indésirable associé à l’utilisation de plusieurs antibiotiques, dont la pipéracilline-tazobactam (P/T). Des données récentes indiquent que le risque de neutropénie chez les enfants est significativement plus élevé avec la P/T qu’avec l’association ticarcilline-clavulanate. Objectifs : Comparer le risque de neutropénie associé à la P/T et à la céfazoline chez une population adulte et décrire les caractéristiques des épisodes de neutropénie observés. Méthodes : Cette étude rétrospective descriptive impliquait des patients âgés d’au moins 18 ans ayant reçu un traitement d’au moins 10 jours par P/T ou céfazoline entre janvier 2009 et décembre 2013. Les patients ayant présenté une neutropénie (nombre absolu de neutrophiles