一位服用 metformin 的第二型糖尿病病人預定接受心導管檢查，檢查會經動脈注射含碘對比劑；病人的基礎腎功能正常。護理師應預期關於 metformin 的哪一項處置？
A client with type 2 diabetes mellitus who takes metformin is scheduled for a cardiac catheterization with intra-arterial iodinated contrast. The client's baseline renal function is normal. Which action regarding the metformin should the nurse anticipate?
- AGive the client's usual morning dose of metformin on the day of the procedure as scheduled檢查當天早上照常給予病人平常劑量的 metformin
- BWithhold metformin at the time of the procedure and for 48 hours afterward, restarting it after renal function is rechecked在檢查當時停用 metformin 並於檢查後持續停用 48 小時，待重新檢驗腎功能後再恢復正確答案
- CWithhold metformin for 48 hours before the procedure and restart it as soon as the procedure is finished檢查前 48 小時停用 metformin，檢查一結束就立刻恢復服用
- DDiscontinue metformin permanently after the procedure and change the client to insulin therapy檢查後永久停用 metformin，改為胰島素治療
- B在檢查當時停用 metformin 並於檢查後持續停用 48 小時，待重新檢驗腎功能後再恢復
正確答案是 B。含碘對比劑可能造成對比劑相關急性腎損傷；腎功能一旦下降，metformin 排除減少而在體內蓄積，乳酸中毒的風險隨之上升。美國 FDA 2016 年的仿單更新指出，接受動脈內含碘對比劑的病人（心導管即屬此類），以及 eGFR 介於 30 至 60、有肝病、酗酒或心衰竭病史者，應在檢查當時或之前停用 metformin，於檢查後 48 小時重新評估 eGFR，確認腎功能穩定才恢復用藥；ACR 對比劑手冊的建議一致。A：動脈內對比劑屬於必須停藥的情境，不可照常給藥。C：方向相反，風險發生在對比劑注射之後，必須停藥的是檢查後的 48 小時；檢查一結束就恢復，會忽略腎功能可能在這段期間惡化。D：腎功能確認穩定後即可繼續使用，不需要永久停藥或改用胰島素。護理師另需依醫囑鼓勵補充水分、監測尿量與腎功能，並向病人清楚說明何時可以恢復服藥。來源：U.S. FDA Drug Safety Communication on metformin-containing drugs（2016）與 metformin 仿單；ACR Manual on Contrast Media（Metformin 章節）。
- A檢查當天早上照常給予病人平常劑量的 metformin
錯誤。心導管使用動脈內含碘對比劑，屬於 FDA 與 ACR 都要求停藥的情境，照常給藥會在腎功能下降時使藥物蓄積。
- B · 正確答案在檢查當時停用 metformin 並於檢查後持續停用 48 小時，待重新檢驗腎功能後再恢復
正確。檢查當時停藥並持續停用 48 小時，之後重新檢驗腎功能，確認穩定才恢復，符合 FDA 仿單與 ACR 對比劑手冊。
- C檢查前 48 小時停用 metformin，檢查一結束就立刻恢復服用
錯誤。風險發生在對比劑注射之後，必須停藥的是檢查後 48 小時；一結束就恢復會忽略腎功能可能在這段期間惡化。
- D檢查後永久停用 metformin，改為胰島素治療
錯誤。只要 48 小時後複驗腎功能穩定就可以恢復 metformin，不需要永久停藥，也不必改為胰島素治療。
美國依 FDA 仿單與 ACR 手冊分類，靜脈注射對比劑且腎功能正常者多不再常規停用 metformin；台灣許多醫院的檢查前評估表仍要求所有服用 metformin 的病人於檢查後停藥 48 小時並複驗腎功能，護理師需依各院規範執行並向病人說明恢復用藥的時間。
English explanation
Option B is correct. Iodinated contrast can cause contrast-associated acute kidney injury, and if renal function falls, metformin is cleared less effectively, accumulates, and raises the risk of lactic acidosis. The 2016 FDA labeling update directs that metformin be stopped at the time of, or before, an iodinated contrast procedure in clients who receive intra-arterial contrast, which includes cardiac catheterization, and in clients with an eGFR of 30 to 60 or a history of liver disease, alcohol use disorder, or heart failure. The eGFR is re-evaluated 48 hours after the procedure, and metformin is restarted only if renal function is stable; the ACR Manual on Contrast Media gives the same direction. Option A is incorrect because intra-arterial contrast is one of the situations in which the drug must be held. Option C is incorrect because the risk follows the contrast injection, so the required interval is after rather than before the procedure, and restarting immediately ignores the possibility that renal function will worsen within 48 hours. Option D is incorrect because metformin is resumed once renal function is stable and does not have to be stopped permanently or replaced with insulin. The nurse also encourages prescribed hydration, monitors urine output and renal studies, and tells the client when the drug may be resumed. Source: U.S. FDA Drug Safety Communication on metformin-containing medicines (2016) and the metformin prescribing information; ACR Manual on Contrast Media (metformin section).