Warfarin 是廣泛使用之口服抗凝血劑，主要經由cytochrome P450(CYP 450)所代謝，容易發生藥物交互作用。本案例是一位有心房纖維顫動(atrial fibrillation, AF)病史，長期服用warfarin 來調控凝血功能的99 歲婦女。本次因為腸胃炎而住院，醫師給予抗生素ciprofloxacin 進行治療，卻在治療過程中發現病患的國際標準凝血時間比(international normalized ratio, INR)異常升高，遂依處理原則建議立即停止服用warfarin，且密切監測患者的INR 值；但是發現warfarin 停用之後，病患的INR 值沒有降低反而是持續升高，因此懷疑即使在warfarin 停用之後，改使用抗生素metronidazole 進行治療，可能仍會有藥物交互作用的問題存在。同時，個案入院後因身體不適而不願進食，使得營養攝取不足，造成白蛋白(albumin)偏低，也可能是影響INR 值持續升高的危險因子。
 

 

Warfarin is an extensively used oral anticoagulant, primarily metabolized by hepatic microsomal enzymes cytochrome P450 (CYP450). Many drugs potentially interact with warfarin. This is a case of 99-year-old woman with atrial fibrillation who was treated with warfarin for a while. She was admitted to the hospital for acute gastroenteritis and treated with ciprofloxacin. During treatment, her international normalized ratio (INR) was out of the therapeutic range, warfarin was stopped immediately. But after the cessation of warfarin, her INR continued to rise. We suspected that the use of metronidazole after stopping warfarin may still inhibit the metabolism of warfarin. In addition, because of her poor nutrition during hospitalization, the albumin level was low, that may be a risk factor to cause the rise in INR.