akinohanayuki ブログ

学位を持っても、センスのない、感染制御専門薬剤師のブログ.  I have Ph.D. but less sense ID pharmacist.

心房細動と抗凝固

循環器科以外では、AFに抗凝固の処方忘れ症例も多いです。
WarfarinやNOACの処方提案を主治医と議論する事は、重要ですね。
その際に、CHA2DS2-VAScやHAS-BLEDも含めた議論は、はじめの一歩です。

以下、UpToDate より

Indications — Anticoagulant therapy is effective in reducing the risk of systemic embolization in patients with nonvalvular atrial fibrillation (AF). Anticoagulation with warfarin, dabigatran, rivaroxaban, apixaban, or edoxaban reduces this risk by almost 70 percent, and should be considered for most nonvalvular AF patients. However, the use of anticoagulant therapy is also associated with an increased risk of major bleeding. While the benefit outweighs the risk in most patients, careful consideration of the risk-to-benefit ratio is necessary in those at relatively very low (CHA2DS2-VASc score of 0) and low risk (CHA2DS2-VASc score of 1).

Our recommendations for anticoagulant therapy in patients with nonvalvular AF are as follows.

●For patients with a CHA2DS2-VASc score ≥2 ,we recommend chronic anticoagulation (Grade 1A).
●For patients with a CHA2DS2-VASc score of 1, our authors and reviewers have differing approaches, with some recommending no antithrombotic therapy and some recommending oral anticoagulant therapy. The risk factor present may influence decision making. Age 65 to 74 years is a stronger risk factor than the other features conferring a CHA2DS2-VASc score of 1.
●For patients with a CHA2DS2-VASc of 0, we suggest no anticoagulant therapy (Grade 2C). Patients who are particularly stroke averse and who are at low bleeding risk may reasonably choose anticoagulation.

Choice of agent — For those patients who receive antithrombotic therapy, we almost always choose an oral anticoagulant rather than aspirin (or any other antiplatelet regimen). For most patients, we have no confidence that the use of aspirin alone is associated with net clinical benefit. 

●In patients with nonvalvular AF for whom anticoagulant therapy is chosen, we suggest an oral direct thrombin inhibitor or a factor Xa inhibitor rather than warfarin (Grade 2B). The evidence does not allow for us to prefer one non-vitamin K antagonist oral anticoagulant (NOAC) agent to another. Thus, we suggest that practitioners become familiar with and comfortable using at least one NOAC agent. 

Warfarin is a reasonable choice in the following circumstances:
•Patients already on warfarin who are comfortable with periodic international normalized ratio (INR) measurement and whose INR has been relatively easy to control, with time in therapeutic range of at least 70 percent.
•Patients who are not likely to comply with the twice daily dosing of dabigatran and apixaban, and for whom once-a-day rivaroxaban or edoxaban is not available.
•Patients for whom the cost of the non-vitamin k antagonist anticoagulants is an important concern.
•Patients with chronic severe kidney disease, whose estimated glomerular filtration rate is less than 30 mL/min/1.73m2 (less than 25 mL/min/1.73m2 for apixaban). 
•Patients for whom NOACs are contraindicated, including those on enzyme-inducing antiepileptic drugs (eg, phenytoin) and patients with human immunodeficiency virus infection (HIV) on protease inhibitor-based antiretroviral therapy.

For the rare patient who cannot take anticoagulant therapy for reasons other than bleeding risk, we suggest aspirin 75 to 100 mg daily plus clopidogrel 75 mg daily, rather than aspirin alone (Grade 2B). 

Dabigatran, rivaroxaban, apixaban, and edoxaban should not be used in patients with severely impaired renal function (estimated glomerular filtration rate less than 30 mL/min/1.73m2 for dabigatran and rivaroxaban; less than 25 mL/min/1.73m2 for apixaban), those with prosthetic heart valves, those with mitral stenosis, or those with other valvular lesions associated with moderate to severe heart failure that might lead to valve replacement in the near future. Edoxaban should also not be prescribed for patients with a creatinine clearance greater than 95 mL/min.

Dosing

For patients prescribed warfarin, we recommend a target INR between 2.0 and 3.0, as opposed to values below or above this range (Grade 1B). 
●For patients prescribed one of the NOACs, we suggest that clinicians review dosing recommendations made by regulatory agencies and available in reputable drug information compendia such as Lexi-Comp.