治療Clostridium difficile 引起的感染，目前建議的首選藥品為口服vancomycin，若擔心病人因有特殊情況而造成腸道內藥品濃度不足時，結腸內給藥可以作為輔助治療。過去認為vancomycin 分子量大且口服後測出的血中濃度常低於治療範圍，臨床上並不會常規監測；然而，陸續有文獻報告提出血管外投與vancomycin 造成全身性血中濃度上升之案例，而目前已知的明確風險因素包含高劑量給藥、長時間使用、嚴重腸道發炎、腎功能不全等。本文報告一腎衰竭之病人，在治療由Clostridium difficile 引起的結腸炎過程中，因合併使用口服與結腸內投與vancomycin，導致測得過高之vancomycin 波谷濃度。希望藉由此案例提醒醫療人員，若腎功能不全合併結腸炎的病人併用2 種給藥途徑時，可主動介入藥品血中濃度監測，以避免發生vancomycin 體內蓄積而引起不良反應。

Oral vancomycin is the first choice for treating Clostridium difficile infection (CDI). However, standard treatment with oral vancomycin fails in a few patients due to inadequate intracolonic drug concentration. Therefore, vancomycin retention enemas can be administered as adjuvant therapy. Therapeutic drug monitoring (TDM) is not necessary during oral vancomycin treatment because of its poor bioavailability. Evidence has shown that the plasma level of vancomycin after oral administration is within or lower than the therapeutic range. However, studies have shown that extravascular administration of vancomycin considerably increases the plasma level of vancomycin. There are some risk factors for systemic exposure to vancomycin, such as high-dose administration, prolonged use, severe inflammatory conditions of the gastrointestinal tract, and renal dysfunction. We report the case of an 85-year-old patient with CDI and renal failure who received high-dose oral vancomycin for a long period in combination with intracolonic drug administration for several days. A supratherapeutic serum level of vancomycin was observed. Therefore, to prevent adverse drug events, TDM should be considered for extravascular administration of vancomycin in patients with severe colitis and renal insufficiency.