1例79岁男性患者因头部外伤合并大肠埃希菌肺炎给予哌拉西林钠他唑巴坦钠4.5 g静脉滴注、1次/8 h治疗。治疗前白细胞计数（WBC）10.20×10n 9/L，红细胞计数（RBC）3.58×10n 12/L，血红蛋白（Hb）101 g/L，血小板计数（PLT）202×10n 9/L。用药第2天，血细胞值开始下降，WBC、RBC、Hb和PLT的最低值分别为2.96×10n 9/L、2.40×10n 12/L、66 g/L和128×10n 9/L。因患者同时出现胃液隐血阳性，而被误诊为消化道出血。但患者无明显黑便，胃液隐血与贫血的发展不成比例，且无溶血和其他部位出血的证据，考虑可能与哌拉西林钠他唑巴坦钠有关。停用该药，3 d后患者的血细胞均恢复到治疗前的水平。n “,”A 79-year-old male patient was given an IV infusion of piperacillin sodium and tazobactam sodium 4.5 g once every 8 hours for head injury complicated by n Escherichia coli pneumonia. Before the treatment, his white blood cell count (WBC) was 10.20×10n 9/L, red blood cell count (RBC) was 3.58×10n 12/L, hemoglobin (HB) was 101 g/L, and platelet count (PLT) was 202×10n 9/L. On day 2 of medication, his blood cell count began to decrease, with the lowest values of WBC 2.96×10n 9/L, RBC 2.40×10n 12/L, Hb 66 g/L, and PLT 128×10n 9/L, respectively. It was misdiagnosed as gastrointestinal bleeding because of positive occult blood in gastric juice of the patient at the same time. However, the patient had no obvious melena, his gastric fluid occult blood did not match the development of anemia, and there was no evidence of hemolysis or hemorrhage at other sites. The relationship between the blood cell count decrease and piperacillin sodium and tazobactam sodium was considered. The drug was discontinued and the patient′s blood cell count returned to levels before treatment 3 days later.n