A Review on the New and Old Anticoagulants.

Anticoagulants serve as the primary strategy for the prevention and treatment of both arterial and venous thromboembolism. Anticoagulants disrupt coagulation by interfering at various points in the coagulation cascade. This class of medications does not lyse clots that already exist; rather, it prevents thrombus formation and prevents or slows the extension of an existing clot. For decades, the standard therapy for patients requiring oral anticoagulation was warfarin. However, due to some of the shortcomings of warfarin, including the need for continuous routine monitoring, longtime onset and offset of anticoagulation effect, major food and drug interactions, and high incidence of bleeding, newer agents, termed direct oral anticoagulants, or DOACs were developed. This article will provide a review of clinically important information regarding the most commonly used anticoagulants and their reversal agents.

Drug Class, Renal Elimination, and Outcomes of Direct Oral Anticoagulants in Asian Patients: A Meta-Analysis.

BACKGROUND: Direct oral anticoagulants (DOACs) have a better risk benefit profile in Asian patients with atrial fibrillation (AF). Whether treatment effects could be modified by drug class and dependency on renal elimination of studied agents has not yet been explored. METHODS: We searched PubMed, CENTRAL, and CINAHL databases through November 2016 for phase III randomized controlled trials comparing DOACs with warfarin in patients with AF. Efficacy and safety outcomes were pooled according to drug class and dependency on renal elimination of DOACs and were compared with the Mantel-Haenszel fixed-effects model. Effect differences were assessed with Bucher's indirect comparisons using common estimates, once heterogeneity was low, and with the Bayesian method. RESULTS: Among 6496 Asian patients from 6 trials, both direct thrombin inhibitors and factor Xa inhibitors, compared with warfarin, were associated with lower risks of stroke or systemic embolism and major bleeding (risk ratio [95% confidence interval], 0.51 [0.33-0.78], 0.74 ([0.58-0.96], 0.60 [0.41-0.86], and 0.59 [0.47-0.76], respectively). There was no between-group difference in direct thrombin inhibitors and factor Xa inhibitors or in DOACs with renal elimination less than 50% and 50% or greater (all I2 < 25% and interaction P > .05). Indirect comparisons within strata of drug class and dependency on renal elimination showed no preferential effect of any given regimen over another. There was no difference in effects on ischemic and hemorrhagic stroke, intracranial hemorrhage, myocardial infarction, and all-cause mortality between DOACs stratified by pharmacologic characteristics. CONCLUSIONS: DOACs, as a therapeutic class, outperform warfarin in efficacy and safety in Asian patients with AF.

High-performance liquid-chromatographic determination of warfarin enantiomers in plasma with automated on-line sample enrichment.

A sensitive and selective chiral high performance liquid chromatographic method was developed for the direct determination of R- and S-warfarin enantiomers in human plasma. The method involved direct injection of human plasma onto a semipermeable surface (SPS) guard column, washing the proteins from the column with aqueous acetonitrile and back flushing the analytes onto a reversed phase ovomucoid silica HPLC column using switching valves. After separation, the analytes were simultaneously detected and quantitated with a fluorometer. The recoveries of R-warfarin from human plasma at 25 and 2500 ng/ml were 98.9% and 88.1%, respectively. The recoveries of S-warfarin at 25 and 2500 ng/ml were 105.4% and 93.9%, respectively. Using 100 microl of human plasma, the lower limit of quantification for both R- and S-warfarins was 25 ng/ml. Linear responses in analyte/internal standard peak height ratios were observed for analyte concentrations ranging from 25 to 2500 ng/ml for both enantiomers. Fluorescence chromatograms of drug-free human plasma showed no interfering peaks with retention times similar to those for R- and S-warfarins and the internal standard. Results from a 3-day validation study for both enantiomers demonstrated excellent precision (1.7-9.0%) and accuracy (97-109%) across the calibration range.

Insight into the chiral recognition of warfarin enantiomers by epichlorhydrin/beta-cyclodextrin polymer-based supports: determination of stoichiometry and stability of warfarin/beta-cyclodextrin polymer complexes.

The complexation of warfarin (W) enantiomers by a hydrosoluble high-molecular-weight beta-cyclodextrin/epichlohydrin polymer (EP/beta-CD polymer) was studied using HPLC with a mobile phase of methanol/0.1 M Na acetate/acetic acid (pH 4) at 22 degrees C. It was found that the complexes (W/beta-CD unit) have a 1:1 stoichiometry. The stability constants of the complex involving each enantiomer and the polymer beta-CD units were determined in the mobile phase, and the highest stability of the complex (S-warfarin/beta-CD unit) was observed. From the chromatographic separations of warfarin enantiomers on different beta-CD or its derivative supports, we have deduced the role of the simultaneous presence of several glyceryl (-O-CH(2)-CHOH-CH(2)-O-) and dihydroxypropyl (-O-CH(2)-CHOH-CH(2)OH) groups on one beta-CD ring in promoting the chiral recognition of warfarin enantiomers.