Thrombocytopenia and anemia associated with piperacillin-tazobactam: integrating clinical case series with FAERS disproportionality analysis.

Background: Piperacillin-tazobactam (TZP) is a commonly used broad-spectrum antibiotic in clinical practice; however, its haematopoietic toxicity profile has not yet been fully elucidated. This study combines clinical case observations with large-scale pharmacovigilance data to characterize TZP-associated thrombocytopenia and anemia. Methods: We first report a case series of three patients presenting with distinct TZP-associated haematopoietic injuries, including severe thrombocytopenia complicated by mild anemia, as well as mixed haematopoietic toxicity predominantly manifested as anemia, with or without concomitant thrombocytopenia. Subsequently, a disproportionality analysis was performed on the FDA Adverse Event Reporting System (FAERS) database using four quantitative methods: Reporting Odds Ratio (ROR), Proportional Reporting Ratio (PRR), Bayesian Confidence Propagation Neural Network (BCPNN), and Multi-item Gamma Poisson Shrinker (MGPS). Results: The disproportionality analysis confirmed a significant and robust risk signal for TZP-associated thrombocytopenia (ROR = 5.26, 95% CI 4.81-5.74), which remained stable in sensitivity analyses adjusting for concomitant medications. Although the signal for anemia was relatively weak across all methods, the clinical cases provided key evidence supporting the occurrence of this adverse reaction. Conclusion: TZP can induce severe thrombocytopenia. It is recommended to actively monitor complete blood counts, with particular attention to platelet, erythrocyte, and hemoglobin levels, within the first week of treatment initiation. When encountering unexplained cytopenia in clinical practice, TZP should be considered as a potential causative agent; if the drug is highly suspected, immediate discontinuation is warranted.