Piperacillin-tazobactam (PTZ) 為一廣效性複方抗生素，廣泛用於感染的經驗性抗生素。常見的藥物不良反應為胃腸不適、皮膚過敏反應及中樞神經症狀如頭痛失眠等。血液方面的不良反應包括嗜中性白血球減少症 (neutropenia)、白血球減少症(leukopenia)，而血小板減少症 (thrombocytopenia) 屬於少見副作用，在文獻中僅有少數的案例報告。本案例為一名81 歲長者因肺炎導致呼吸衰竭而入院，使用PTZ 後血小板逐漸下降，至第17 天降至最低點，血小板數量為7,000/μL，停藥及輸注血小板後3 天，血小板上升至162,000/μL。依據文獻查證，PTZ 造成的獨立性血小板減少是經由免疫介導，再次接觸可能導致更嚴重之反應。藉由此案例提醒醫療人員，使用PTZ 須定期監測病人血球變化，若發生不良反應時應先停用疑似藥物，確認藥物的相關性後應登錄於病歷，以防止再次接觸造成更嚴重的傷害。

Piperacillin-tazobactam (PTZ) is a broad-spectrum antibiotic that is widely used as an empiric antibiotic to treat infections. Common adverse drug reactions include gastrointestinal discomfort, skin allergic reactions, and central nervous system symptoms such as headache and insomnia. Hematological complications include neutropenia and leukopenia. Thrombocytopenia is a rare adverse event and only a few case reports exist in the literature. This report describes the case of an 81-year-old person who was admitted to the hospital for respiratory failure caused by pneumonia. After PTZ was administered, the platelets gradually decreased and reached a nadir on the 17th day, when the platelet count was 7,000/μL. After PTZ administration was withdrawn and platelet transfusion was provided, the platelets increased to 162,000/μL 3 days later. According to the literature, isolated thrombocytopenia caused by PTZ is immune-mediated, and re-exposure may cause more serious reactions. This case should remind medical staff that when PTZ is used, they must regularly monitor the patient’s complete blood count. If an adverse drug reaction occurs, the suspected drug should first be stopped, and the relevance of the drug should be registered in the medical record to prevent further serious injury caused by re-exposure.