護理師準備給予病人預定的華法林（warfarin）劑量。給藥前必須評估哪個實驗室數值？
A nurse is preparing to administer a scheduled dose of warfarin to a client. Which laboratory value must the nurse assess before administration?
- ASerum creatinine血清肌酸酐
- BPlatelet count血小板計數
- CProthrombin time (PT) / International Normalized Ratio (INR)✓ 正解凝血酶原時間 (PT) / 國際標準化比值 (INR)
- DHemoglobin A1c糖化血色素 (Hemoglobin A1c)
華法林（Warfarin）是一種維生素 K 拮抗劑，透過抑制肝臟合成依賴維生素 K 的凝血因子來達到抗凝血效果。其藥效範圍窄且受飲食、藥物交互作用影響大，因此必須透過監測凝血酶原時間（PT）及其國際標準化比值（INR）來調整劑量，以確保在治療範圍內，避免發生出血或血栓。給藥前若未確認 INR，極易導致病人暴露於出血風險中。
Warfarin is a vitamin K antagonist that produces its anticoagulant effect by inhibiting hepatic synthesis of vitamin K-dependent clotting factors. Because of its narrow therapeutic window and substantial interactions with diet and other medications, the dose must be adjusted based on monitoring of prothrombin time (PT) and the International Normalized Ratio (INR) to ensure the value remains within therapeutic range and to avoid bleeding or thrombosis. Failure to verify the INR before administration places the client at risk for bleeding.