Use of Thromboelastography (TEG) for Detection of New Oral Anticoagulants.

CONTEXT: The clinical introduction of new oral anticoagulants (NOACs) has stimulated the development of tests to quantify the effects of these drugs and manage complications associated with their use. Until recently, the only treatment choices for the prevention of venous thromboembolism in orthopedic surgical patients, as well as for stroke and systemic embolism in patients with atrial fibrillation, were vitamin K antagonists, antiplatelet drugs, and unfractionated and low-molecular-weight heparins. With the approval of NOACs, treatment options and consequent diagnostic challenges have expanded. OBJECTIVE: To study the utility of thromboelastography (TEG) in monitoring and differentiating between 2 currently approved classes of NOACs, direct thrombin inhibitors (dabigatran) and factor Xa inhibitors (rivaroxaban and apixaban). DESIGN: Blood samples from healthy volunteers were spiked with each NOAC in both the presence and absence of ecarin, and the effects on TEG were evaluated. RESULTS: Both the kaolin test reaction time (R time) and the time to maximum rate of thrombus generation were prolonged versus control samples and demonstrated a dose response for apixaban (R time within the normal range) and dabigatran. The RapidTEG activated clotting time test allowed the creation of a dose-response curve for all 3 NOACs. In the presence of anti-Xa inhibitors, the ecarin test promoted significant shortening of kaolin R times to the hypercoagulable range, while in the presence of the direct thrombin inhibitor only small and dose-proportional R time shortening was observed. CONCLUSIONS: The RapidTEG activated clotting time test and the kaolin test appear to be capable of detecting and monitoring NOACs. The ecarin test may be used to differentiate between Xa inhibitors and direct thrombin inhibitors. Therefore, TEG may be a valuable tool to investigate hemostasis and the effectiveness of reversal strategies for patients receiving NOACs.

Simultaneous determination of a hydrophobic drug candidate and its metabolite in human plasma with salting-out assisted liquid/liquid extraction using a mass spectrometry friendly salt.

In previously reported applications of salting-out assisted liquid/liquid extraction (SALLE) with acetonitrile, only inorganic salts were evaluated and implemented as the salting-out reagents. A potential concern of the method for the subsequent LC-MS analysis of biological samples was that a portion of the added salt (typically of high concentration) might be extracted and affect the chromatography separation and ionization of chromatography effluents in a mass spectrometer. Here we report, for the first time, the use of a mass spectrometry friendly organic salt, ammonium acetate, as a salting-out reagent in SALLE with acetonitrile for the simultaneous quantitation of an Abbott investigational new drug ABT-869 and its hydrophilic metabolite in human plasma. The performance of SALLE with ammonium acetate was compared with that of a previously reported method with a conventional liquid/liquid extraction technique using a set of pooled incurred samples. The % differences of the measured concentrations for 24 samples from these two methods were found to be within acceptance criteria, demonstrating SALLE with ammonium acetate as a reliable sample preparation technique. The SALLE method is simple, fast (25 min/plate), easy for automation, free of drying down step, and environmentally friendly. SALLE with mass spectrometry friendly salts has been applied to regulated sample analysis of both hydrophilic and hydrophobic compounds. It is envisioned that SALLE with acetonitrile and ammonium acetate be a universal method for high throughput automated sample preparation for bioanalytical chemistry.