Description

Non-vitamin K antagonist oral anticoagulants (NOACs) are recommended over warfarin in preventing stroke and thromboembolism among patients with atrial fibrillation (AF) in several guidelines. To evaluate the pharmacological effects of NOACs, directly measuring the concentration is the most arbitrary way since the correlation between concentration and common coagulation tests are not reliable. Our previous investigation reported under the fixed dose regimen, dabigatran exposure increased in elderly, renal impairments and patients with multiple co-morbid conditions. Our data also showed difference in NOACs exposure in Asians. For example, patients under rivaroxaban, in comparison to apxiaban, were more likely to have lower than expected range drug level. Furthermore, the NOACs concentration also affected by the prescription pattern of physicians (non-compliant to labeled dose) and patients' behavior (poor medication adherence).

The relationship between NOACs exposure and safety has been elucidated in large-scale clinical trials. As the NOACs level increased, the risk for bleeding increased, too. Nevertheless, no additional protection was noted with increased NOACs levels. In post marketing surveillance, bleeding and thrombotic events have been reported. Investigating the NOACs level among these patients helps evaluating the residual drug in the body, which could be a reference for clinical decision in emergent situation.

Specific purpose:

1. Prospectively record the NOACs concentration among AF patients under NOACs therapy and suffered from IS, TIA, ICH or major bleeding.

AF patients who presented to emergent department (ED) for acute IS, TIA, ICH (non-traumatic), or other major bleeding and was under NOACs therapy will be recruited to this study. Blood sample will be collected before acute management to measure NOACs concentration. Co-morbid disease, laboratory tests and concurrent medications will be retrieved from electronic medical records. The onset, location, severity of IS. ICH or other major bleeding, and the outcome and long-term managements will be prospectively recorded.

2. Investigate the correlation between NOACs concentration and thromboembolic or bleeding events.

For each NOACs, we are going to compare the differences in NOACs exposure between patients with thromboembolism or major bleedi. Important baseline characteristics, co-medications and disease severity will be adjusted before making comparison.

3. Propose a therapeutic range for NOACs, in order to provide a guide for important decision in acute setting.

From the data of NOACs concentration among patients with IS or ICH, we plan to propose a therapeutic range with acceptable efficacy and safety for NOACs therapy. Our data will provide a guide for physicians to make important clinical decision.