71.若病人服藥adherence良好，下列何者最可能有「藥品劑量不足」的問題？
(A)55歲hypertension病人（無其他疾病），服用amlodipine 5 mg QD一個月後，測得血壓135/80 mmHg
(B)60歲type 2 DM病人，服用metformin 500 mg QD三個月後，測得Hb7.8%
(C)65歲atrial fibrillation病人，服用warfarin 5 mg QD二星期後，測得INR 3.2
(D)70歲grand mal seizure病人服用phenytoin 300 mg QD 一個月後，測得phenytoin血中濃度22 mg/L

INR

正常人INR:0.8-1.2，病人服用wafarin後，INR應介於2至4之間

HbA1c

一般來說， HbA1c的正常檢測參考值約為4%~6%，國際間採用之糖尿病治療準則是將HbA1c控制在7%以下

(C) AF患者的INR控制在2-3，此患者INR 3.2 ->劑量稍高

Vitamin K antagonist — For patients with AF treated with VKA (eg, warfarin), an INR between 2.0 and 3.0 is recommended with an average annual TTR >70 percent [21,22]. This is based upon the increased risk of stroke observed with INR values significantly below 2 (four- to sixfold at an INR of 1.3 compared with an INR of 2 or above) and the increased risk of bleeding associated with INR above 3.0 .

Advanced age(over 74 years) is an independent risk factor for bleeding during anticoagulation as well as a risk factor for stroke. However, we recommend an INR between 2.0 and 3.0 for these patients as well 

REF: UpToDate - Atrial fibrillation in adults: Use of oral anticoagulants

補充TTR (time in therapeutic range)：如TTR 65%代表患者在治療期間平均有65%的時間維持在治療範圍之內，許多大型試驗利用來評估口服抗凝血劑的治療成果和品質，TTR愈高，中風、出血、死亡的發生率愈低。

資料來源：新型口服抗凝血劑 - 心房顫動中風預防的新曙光