Piperacillin-Tazobactam Strikes Again: A Neutropenic Mystery Unraveled.

Piperacillin-tazobactam is a broad-spectrum antibiotic commonly used in inpatient settings, particularly for febrile neutropenia. While its known adverse effects are mainly gastrointestinal, rare hematologic effects have been reported. This case describes a patient who developed leukopenia and severe neutropenia after prolonged use of piperacillin-tazobactam. A male in his 60s was transferred to our facility for specialized care following Hartmann's procedure for an obstructing sigmoid mass. He was on piperacillin-tazobactam for suspected sepsis. After 24 days of therapy, he developed severe neutropenia without signs of infection or other underlying causes. Hematology evaluation ruled out alternative explanations, and piperacillin-tazobactam was identified as the probable cause. Upon discontinuation, his blood counts gradually improved without requiring granulocyte colony-stimulating factor (G-CSF) support. Leukopenia due to piperacillin-tazobactam is rare and likely dose- and duration-dependent, potentially caused by direct toxicity to myeloid precursors. Other hematologic effects like hemolytic anemia and thrombocytopenia have been documented. Prolonged use of piperacillin-tazobactam, especially in at-risk groups, can lead to hematologic toxicity. Clinicians should monitor blood counts during extended therapy and consider early discontinuation if adverse effects arise.