Pharmacology of the new target-specific oral anticoagulants

Transitioning between therapeutic anticoagulants: a clinicians guide to switching patients to or from DOAC therapy

INTRODUCTION

The transition to or from direct oral anticoagulants (DOACs) is common in clinical practice.

AREAS COVERED

A literature search was conducted on PubMed, Google Scholar, and UpToDate up to March 2024 for conditions and approaches for transitioning from one agent to the other. No randomized clinical trials were retrieved except for two studies regarding switching to DOAC in well-conducted vitamin K antagonist (VKA) therapy. A narrative review was conducted addressing the conditions for switching from one agent to the other, such as thromboembolic events and major bleeding during anticoagulation, development or worsening of kidney or liver failure, initiation of interfering drugs, adverse events such as allergic reactions, frailty, patients' preferences, and affordability. During transitions from one anticoagulant to the other, the risk of both thromboembolic and bleeding complications should be minimized. The current approaches for such transitions are derived from those employed in clinical trials evaluating DOAC and from product information.

EXPERT OPINION

Many uncertainties remain regarding those circumstances requiring a change in anticoagulant strategies, as they lack evidence-based guidance. It can be envisaged that the problem of switching to and from DOAC will need additional studies especially addressing the conditions and the best approach to such transitions.

Drug-drug interactions with oral anticoagulants: information consistency assessment of three commonly used online drug interactions databases in Switzerland

Background: Toxicity or treatment failure related to drug-drug interactions (DDIs) are known to significantly affect morbidity and hospitalization rates. Despite the availability of numerous databases for DDIs identification and management, their information often differs. Oral anticoagulants are deemed at risk of DDIs and a leading cause of adverse drug events, most of which being preventable. Although many databases include DDIs involving anticoagulants, none are specialized in them. Aim and method: This study aims to compare the DDIs information content of four direct oral anticoagulants and two vitamin K antagonists in three major DDI databases used in Switzerland: Lexi-Interact, Pharmavista, and MediQ. It evaluates the consistency of DDIs information in terms of differences in severity rating systems, mechanism of interaction, extraction and documentation processes and transparency. Results: This study revealed 2'496 DDIs for the six anticoagulants, with discrepant risk classifications. Only 13.2% of DDIs were common to all three databases. Overall concordance in risk classification (high, moderate, and low risk) was slight (Fleiss' kappa = 0.131), while high-risk DDIs demonstrated a fair agreement (Fleiss' kappa = 0.398). The nature and the mechanism of the DDIs were more consistent across databases. Qualitative assessments highlighted differences in the documentation process and transparency, and similarities for availability of risk classification and references. Discussion: This study highlights the discrepancies between three commonly used DDI databases and the inconsistency in how terminology is standardised and incorporated when classifying these DDIs. It also highlights the need for the creation of specialised tools for anticoagulant-related interactions.

Edoxaban Monotherapy in Nonvalvular Atrial Fibrillation Patients with Coronary Artery Disease

Background

Current guidelines recommend an oral anticoagulant (OAC) monotherapy in patients with nonvalvular atrial fibrillation (NVAF) and stable coronary artery disease (CAD) 1 year postpercutaneous coronary intervention (PCI). It might be possible to shorten the time for de-escalation from a dual therapy to monotherapy, but data regarding de-escalation to an edoxaban monotherapy are lacking. This study aimed to assess the clinical safety of an edoxaban monotherapy in patients with NVAF and stable CAD.

Methods

A multicenter, prospective, randomized, open-label, and parallel group study was established to investigate the safety of an edoxaban monotherapy in patients with NVAF and stable CAD including over 6 months postimplantation of a third-generation DES and 1 year postimplantation of other stents (PRAEDO AF study). Between March 2018 and June 2020, 147 patients from 8 institutions in Japan were randomized to receive either an edoxaban monotherapy (n = 74) or combination therapy (edoxaban plus clopidogrel, n = 73). The primary study endpoint was the composite incidence of major bleeding and clinically significant bleeding, defined according to the ISTH criteria.

Results

Major or clinically significant bleeding occurred in 2 patients in the monotherapy group (1.67% per patient-year) and in 5 patients in the combination therapy group (4.28% per patient-year) (hazard ratio, 0.39; 95% confidence interval, 0.08-2.02). There was no incidence of a myocardial infarction, stent thrombosis, unstable angina requiring revascularization, ischemic stroke, systemic stroke, or hemorrhagic stroke in either of the groups.

Conclusions

The edoxaban monotherapy was shown to have acceptable clinical safety in patients with NVAF and stable CAD. The study was registered with the Japan Registry of Clinical Trials (jRCTs031180119).

Developing LC-MS/MS methods to quantify rivaroxabanin human plasma and urine: application to therapeuticdrug monitoring

Rivaroxaban is an oral anticoagulant directly inhibiting Factor Xa activity, which is widely used for prophylaxis of thromboembolic disorders and is required for therapeutic drug monitoring (TDM) during therapyfor individual dosage adjustment. Thisstudyaimed at developing a liquidchromatography/tandem mass spectrometry method that was suitable forrivaroxaban TDM in human plasma and urine and exploring the feasibility of urine drug monitoring in medical care. The 3-min run of LC-MS/MS methodswereestablishedby employingan Acquity UPLC BEH C₁₈ (2.1 mm × 50 mm, 1.7 μm) column using gradient elution of 10 mmol/L ammonium acetate containing 0.1% formic acid - 0.1% formic acid acetonitrile as mobile phase at a flow rate of 0.4 mL/min with the calibration range of 0.5 ng/mL-400 ng/mL and 10 ng/mL-10000 ng/mLfor human plasma and urine, respectively. Rivaroxaban wasdetected on a triple quadrupole tandem mass spectrometer with electrospray ionization source in positive ion mode. Themethods showed good linearity within the calibration range. Theprecision and accuracy, matrix effect, extraction recovery and stability inboth human matrices were all validatedand meet the international guideline requirements. These validated methods had been successfullyapplied to support TDMofan aged patient receiving rivaroxaban for therapy.

Difference in left atrial D-dimer level in patients with atrial fibrillation treated with direct oral anticoagulant

Background

Atrial fibrillation (AF) may cause cerebral and systemic embolism. An increased D-dimer level indicates hyperactivation of secondary fibrinolysis, resulting in predilection for thrombosis. To clarify the differential effects of anticoagulation therapy, we compared the D-dimer levels in peripheral and left atrial (LA) blood of atrial fibrillation patients scheduled for ablation.

Methods

We analyzed 141 patients with non-valvular AF (dabigatran, n = 30; apixaban, n = 47; edoxaban, n = 64; mean age: 68 years, male: 60%). Peripheral venous blood and LA blood was collected before pulmonary vein isolation. We examined the laboratory and echocardiographic parameters.

Results

After adjusting for baseline characteristics, D-dimer level in the LA was significantly higher in patients treated with edoxaban than that in those on apixaban (0.77 ± 0.05 vs. 0.60 ± 0.05 μg/mL, P = 0.047), although there were no significant differences in peripheral D-dimer levels. We classified the D-dimer value of the LA into a normal group (< 0.9) and a high value group (≥ 1.0); the peripheral prothrombin fragment F1 + 2 level (odds ratio [OR] 1.012; 95% confidence interval [CI]: 1.003–1.022; P = 0.008) and left ventricular ejection fraction (LVEF) (OR, 0.947; 95% CI, 0.910–0.986; P = 0.008) were potential predictors of high LA D-dimer levels.

Conclusions

In apixaban-treated patients, the D-dimer level in the left atrium was lower than in edoxaban-treated patients on the day of ablation, suggesting that the anticoagulant effect of apixaban on the left atrium is better than that of edoxaban in patients with AF.

Mass spectrometry-based targeted proteomics method for the quantification of clinically relevant drug metabolizing enzymes in human specimens

Biotransformation by phase I and II metabolizing enzymes represents the major determinant for the oral bioavailability of many drugs. To estimate the pharmacokinetics, data on protein abundance of hepatic and extrahepatic tissues, such as the small intestine, are required. Targeted proteomics assays are nowadays state-of-the-art for absolute protein quantification and several methods for quantification of drug metabolizing enzymes have been published. However, some enzymes remain still uncovered by the analytical spectra of those methods. Therefore, we developed and validated a quantification assay for two carboxylesterases (CES-1, CES-2), 17 cytochrome P450 enzymes (CYP) (CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C18, CYP2C19, CYP2D6, CYP2E1, CYP2J2, CYP3A4, CYP3A5, CYP3A7, CYP4F2, CYP4F12, CYP4A11) and five UDP-glucuronosyltransferases (UGTs) (UGT1A1, UGT1A3, UGT2B7, UGT2B15, UGT2B17). Protein quantification was performed by analyzing proteospecific surrogate peptides after tryptic digestion with stable isotope-labelled standards. Chromatographic separation was performed on a Kinetex® 2.6 µm C18 100 Å core-shell column (100 × 2.1 mm) with a gradient elution using 0.1% formic acid and acetonitrile containing 0.1% formic acid with a flow rate of 200 µl/min. Three mass transitions were simultaneously monitored with a scheduled multiple reaction monitoring (sMRM) method for each analyte and standard. The method was partly validated according to current bioanalytical guidelines and met the criteria regarding linearity (0.1-25 nmol/L), within-day and between-day accuracy and precision as well as multiple stability criteria. Finally, the developed method was successfully applied to determine the abundance of the aforementioned enzymes in human intestinal und liver microsomes. Our work offers a new fit for purpose method for the absolute quantification of CES, CYPs and UGTs in various human tissues and can be used for the acquisition of data for physiologically based pharmacokinetic modelling.

Relationship of health literacy and adherence to oral anticoagulation therapy in patients with atrial fibrillation: a cross-sectional study

Oral anticoagulant therapy (OAT) has increased substantially due to the aging population and prevalence rise of atrial fibrillation (AF). Medication adherence is important to achieve effectiveness and safety of OAT. The study aim was to investigate the relationship between health literary (HL) and the adherence to OAT in patients with atrial fibrillation (AF). This is a cross-sectional study conducted in a public cardiology clinic in Brazil, 2019. Sociodemographic and clinical data were collected by the review of medical records and interviews with patients. The relation between health literacy (HL) and adherence to OAT was investigated by a multiple logistic regression model. Overall, 100 AF patients were included in this study, with average age of 68.8 ± 13.8 years and predominance of women (54 %). Inadequate HL was found in 79 % of the patients and non-adherence was identified in 66 % of the participants. Sex was the only variable with a statistically significant association with non-adherence to OAT. Men presented a 2.54-fold greater chance of non-adherence to OAT, when compared to the women (Odds ratio (OR) = 2.54; 95 % confidence interval (CI): 1.03-6.62; p = 0.047). No statistically significant relationship was found between inadequate HL and non-adherence to OAT (OR 1.48; 95 % CI, 0.47-4.61; p = 0.49). High rates of inadequate HL and non-adherence to OAT were identified in this study; however, this relationship did not prove to be statistically significant. Further studies are needed to investigate factors associated with non-adherence to OAT in large samples of vulnerable populations and strategies for its improvement in public health.

Rivaroxaban for cancer-associated venous thromboembolism

All cancers can increase the risk of developing venous thromboembolism (VTE), and anticoagulants should be considered as an optimal treatment for patients suffering from cancer-associated VTE. However, there is still a debate about whether the new oral anticoagulant, rivaroxaban, can bring better efficacy and safety outcomes globally. Thus, this systematic review and meta-analysis was conducted to evaluate the efficacy and safety of rivaroxaban. We searched PubMed, Cochrane Central Register of Controlled Trials, Web of Science, and China National Knowledge Infrastructure for relevant published papers before 1 September 2019, with no language restrictions. The primary outcomes are defined as the recurrence of VTE. The secondary outcomes are defined as clinically relevant non-major bleeding, adverse major bleeding events, and all-cause of death. The data were analyzed by Stata with risk ratio (RR) and 95% confidence interval (CI). Four trials encompassing 1996 patients were included. Rivaroxaban reduced recurrent VTE with no significant difference (RR = 0.68, 95% CI = 0.43-1.07). Similarly, there were no significant differences in adverse major bleeding events (RR = 0.86, 95% CI = 0.37-2.00), clinically relevant non-major bleeding (RR = 1.24, 95% CI = 0.73-2.12) and all-cause mortality (RR = 0.76, 95% CI = 0.40-1.44). In a selected study population of cancer patients with VTE, rivaroxaban is as good as other anticoagulants. Further, carefully designed randomized controlled trials should be performed to confirm these results.

Analysis of the Introduction in Clinical Practice of New Oral Anticoagulants in Local Health Agency BT: Translation of the Clinical Trial Data to a Local Health Care Area

The commercial release of the New Oral Anticoagulants (NOACs) has been the most significant change in anticoagulant therapy in recent years. The work aimed to evaluate the economic and health impact for the Local Health Agency Barletta-Andria-Trani (BT). Through the Regional Information System data about naïve patients on NOAC treatment and patients on anti-vitamin-k (VKA), treatments were extrapolated. We assessed therapeutic continuity, pharmaceutical expenditure, hospitalizations, and deaths in 2017 and 2018. Therapeutic continuity was similar in the two groups. The number and the average cost of hospitalizations for a patient treated with VKAs were almost constant, while those of patients treated with NOACs decreased. The treatment of adult-aged naïve patients with NOACs, compared to VKAs therapy, involves an increase in expenditure of about 100€ for a patient, but the reduced hospitalizations could generate, in the long term, saving for the Health System. Clinical data, according to the Real-World Data, confirmed the safety and effectiveness of these drugs. However, attention to the special population is necessary to improve the safety and effectiveness of NOACs. Innovative formulations for pediatric patients are being developed. The challenge for Health Systems is the appropriate use of available resources through health interventions with transversal competences.

Postoperative bleeding after dental extraction among elderly patients under anticoagulant therapy

OBJECTIVES

This study aimed to assess and compare postoperative bleeding occurrence after dental extraction in medically compromised elderly patients under anticoagulant therapy.

MATERIALS AND METHODS

This retrospective study included medically compromised elderly patients aged ≥ 65 years who were taking apixaban, dabigatran, edoxaban, rivaroxaban, or warfarin and had undergone single or multiple dental extractions. The primary outcome measure was postoperative bleeding occurrence, which was defined as oozing or marked hemorrhage from 24 h to 7 days after dental extraction. Postoperative bleeding occurrence was calculated for each anticoagulant and compared using Fisher's exact test, followed by multiple comparisons.

RESULTS

Two hundred thirty-two patients met the inclusion criteria. The highest postoperative bleeding occurrence was recorded for rivaroxaban (12/37: 32.4%), followed by apixaban (8/44: 18.2%), warfarin (17/98: 17.3%), and edoxaban (2/35: 5.7%). Patients taking dabigatran did not present postoperative bleeding (0/18: 0%). Fisher's exact test, followed by multiple comparison tests, revealed a significant among-anticoagulant difference (p = 0.0095). Postoperative bleeding was significantly higher in patients taking rivaroxaban than in those taking edoxaban or dabigatran (p = 0.03088).

CONCLUSIONS

Within the limitations of this retrospective study design, these findings suggest that different anticoagulants may affect postoperative bleeding occurrence after dental extraction among medically compromised elderly patients.

CLINICAL RELEVANCE

Clinicians should carefully consider postoperative bleeding after dental extraction in patients taking anticoagulant therapy, especially rivaroxaban.

The Risks of Exfoliative Esophagitis in Patients with Atrial Fibrillation: A retrospective observational study

The aging of the population has resulted in atrial fibrillation (AF) becoming increasingly prevalent. Treatment focuses on the prevention of thromboembolism through the use of catheter ablation or drug therapy with anticoagulants, such as warfarin or direct oral anticoagulants (DOACs). Dabigatran-induced exfoliative esophagitis has been reported as a rare side effect of DOACs. Although most cases are mild, some result in severe outcomes. However, the etiology of exfoliative esophagitis remains incompletely understood. The aim of this study is to investigate the etiology of exfoliative esophagitis and identify its risk factors by observational study.The participants were 524 patients using anticoagulants who received catheter ablation for AF and subsequently underwent upper gastrointestinal endoscopy at University of Tsukuba Hospital. Exfoliative esophagitis was noted in 21 (4.0%) patients. Potential risk factors for exfoliative esophagitis were examined retrospectively by comparing patients with and without this condition across the following parameters that were extracted retrospectively from the electronic medical records: physical characteristics, comorbidities, blood-based cardiac markers, echocardiographic and endoscopic findings, and current medications.Regarding physical characteristics, patients with exfoliative esophagitis had significantly higher body weight and BMI. No association was observed between exfoliative esophagitis and comorbidities. Associations were also not found for cardiac markers, echocardiographic findings, or endoscopic findings. In terms of current medications, patients receiving oral dabigatran showed the highest prevalence of exfoliative esophagitis at 8.8% (13/148). The adjusted odds ratio of dabigatran for exfoliative esophagitis was 10.3 by multivariable logistic regression analysis.Obesity and oral dabigatran were found to be significant risk factors for exfoliative esophagitis.

Diagnostic performance of coagulation indices for direct oral anticoagulant concentration

INTRODUCTION

Different coagulation indices for direct oral anticoagulants (DOACs) exist in clinical practice, but limited data are available for the diagnostic power of these indices. This review and meta-analysis aims to explore the diagnostic value of coagulation indices for DOACs.

MATERIALS AND METHODS

PubMed, Web of Science, EMBASE, Clinical Trials.gov, and the Cochrane Library were searched from inception of each database to 15 February 2020. Studies reporting a relationship between coagulation indices and the gold standard (liquid chromatography/tandem mass spectrometry) were included in the analysis.

RESULTS

Sixteen articles from 9169 citations evaluating the performance of coagulation indices were included in this review. A total of 236, 273, 273 rivaroxaban samples were included to assess the diagnostic power of anti-Xa activity (AXA), prothrombin time (PT), combined PT and activated partial thromboplastin time, respectively. A total of 268 dabigatran samples were included to assess the diagnostic performance of diluted thromboplastin time (dTT). AXA calibrated by rivaroxaban showed a sensitivity of 0.98 (95% confidence interval (CI): 0.91-0.99) and a specificity of 0.98 (95% CI: 0.94-0.99) at the threshold of 30 ng/mL. For dabigatran, the combined sensitivity of dTT was 0.76 (95% CI: 0.66-0.84) and combined specificity was 0.97 (95% CI: 0.92-0.99).

CONCLUSIONS

DOAC-specific calibrated AXA was a good index to indicate concentration for rivaroxaban and apixaban. More studies on edoxaban and betrixaban are in need. Diluted TT, thrombin inhibitor assay, and ecarin-based assays were potential to measure dabigatran concentration. Due to the limited data, results should be validated in the future.

Emergent cholecystectomy in patients on antithrombotic therapy

The Tokyo Guidelines 2018 (TG18) recommend emergent cholecystectomy (EC) for acute cholecystitis. However, the number of patients on antithrombotic therapy (AT) has increased significantly, and no evidence has yet suggested that EC should be performed for acute cholecystitis in such patients. The aim of this study was to evaluate whether EC is as safe for patients on AT as for patients not on AT. We retrospectively analyzed patients who underwent EC from 2007 to 2018 at a single center. First, patients were divided into two groups according to the use of antithrombotic agents: AT; and no-AT. Second, the AT group was divided into three sub-groups according to the use of single antiplatelet therapy (SAPT), double antiplatelet therapy (DAPT), or anticoagulant with or without antiplatelet therapy (AC ± APT). We then evaluated outcomes of EC among all four groups. The primary outcome was 30- and 90- day mortality rate, and secondary outcomes were morbidity rate and surgical outcomes. A total of 478 patients were enrolled (AT, n = 123, no-AT, n = 355) patients. No differences in morbidity rate (6.5% vs. 3.7%, respectively; P = 0.203), 30-day mortality rate (1.6% vs. 1.4%, respectively; P = 1.0) or 90-day mortality rate (1.6% vs. 1.4%, respectively; P = 1.0) were evident between AT and no-AT groups. Between the no-AT and AC ± APT groups, a significant difference was seen in blood loss (10 mL vs. 114 mL, respectively; P = 0.017). Among the three AT sub-groups and the no-AT group, no differences were evident in morbidity rate (3.7% vs. 8.9% vs. 0% vs. 6.5%, respectively; P = 0.201) or 30-day mortality (1.4% vs. 0% vs. 0% vs. 4.3%, respectively; P = 0.351). No hemorrhagic or thrombotic morbidities were identified after EC in any group. In conclusion, EC for acute cholecystitis is as safe for patients on AT as for patients not on AT.

Association Between the Change in Total Bilirubin and Risk of Bleeding Among Patients With Nonvalvular Atrial Fibrillation Taking Dabigatran

There is still a lack of effective biomarkers for the prediction of the risk of bleeding events among patients with nonvalvular atrial fibrillation (NVAF) taking dabigatran. This study aimed to investigate the association between change in total bilirubin (CTBIL) and risk of bleeding among patients with NVAF taking dabigatran. The CTBIL was the difference in serum total bilirubin at out of follow-up from baseline serum total bilirubin. A total of 486 patients with NVAF treated with dabigatran (110 mg twice daily) were recruited from 12 centers in China from February 2015 to December 2017. All patients were followed for 3 months. Cox proportional hazards regression analysis was used to evaluate the association between the CTBIL and bleeding. Moreover, a Cox proportional hazards regression with cubic spline functions and smooth curve fitting (the penalized spline method) and 2 piecewise Cox proportional hazards models were used to address the nonlinearity between CTBIL and bleeding. The mean (SD) follow-up duration was 81.2 (20.2) days. In all, 67 patients experienced bleeding events. A U-shaped association was observed between the CTBIL and bleeding, with increased hazard ratios (HRs) in relation to either low or high CTBIL levels. For CTBIL <6.63 µmol/L, the HR (95% confidence interval [CI]) was 0.90 (0.84-0.96), and for CTBIL ≥6.63 µmol/L, the HR (95% CI) was 1.35 (1.14-1.60). Our findings showed a U-shaped relationship between CTBIL and bleeding. Both low and high levels of CTBIL were associated with a higher risk of bleeding.

Review of Direct Oral Anticoagulants and Guide for Effective Drug Utilization

Direct oral anticoagulants (DOACs) have been developed as a viable and in some cases superior alternative to warfarin. These agents have overcome some of the limitations of warfarin, which has a narrow therapeutic window and many food and drug interactions. DOACs have been demonstrated to have a more predictable and reliable pharmacology and, unlike warfarin, do not require frequent monitoring of anticoagulant effect. For these reasons, the use of DOACs is increasing. Despite the many positive attributes of these agents, limitations and contraindications do exist. An understanding of the pharmacology, indications, and contraindications is therefore crucial for effective patient management. We review the available agents to aid in effective drug utilization.

Rivaroxaban for cancer-associated venous thromboembolism: A systematic review and meta-analysis protocol

BACKGROUND

All cancers increase developing venous thromboembolism risk, and VTE is the second-leading cause of death among cancer patients. The anticoagulant drugs are considered to be the optimal treatment for patients with cancer-associated VTE. However, there is still controversy whether rivaroxaban, a new oral anticoagulant, can lead to better outcomes globally.

METHODS

We will search PubMed, Web of Science, Cochrane Central Register of Controlled Trials and China National Knowledge Infrastructure for relevant published studies before 1 September, 2019, without any language restrictions. Only published randomized controlled trials that meet the inclusion criteria will be included. Subgroup analysis of the type of cancer, the type of VTE, cancer stage, age, sex, ethnicity, history of smoking and drinking as well as the mean, dose and duration of anticoagulants will be performed.

DISCUSSION

Our study aims to estimate the efficacy and safety of rivaroxaban for patients with cancer-associated VTE and to provide recommendations to key stakeholders.

TRIAL REGISTRATION

PROSPERO, October 23, 2019, CRD42019143265, https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=143265.

Perioperative management of patients with atrial fibrillation receiving anticoagulant therapy

The number of patients with atrial fibrillation (AF) and the number of patients indicated for anticoagulant therapy have been increasing because AF would affect patient survival due to thromboembolism. Once AF develops, following the disappearance of pulsation, the circumstances within the atrium become prothrombotic and thrombus formation within the left atrium occurs in patients with AF. In recent years, not only warfarin but also new oral anticoagulants were introduced clinically and have become used as oral anticoagulants. In the perioperative period, the risk of major hemorrhage needs to be reduced. On the other hand, the suspension of anticoagulant therapy and neutralization of anticoagulant effects elevate the risk of thrombosis. The perioperative management of patients receiving anticoagulant therapy is different from that of scheduled surgery and emergency surgery. In addition, knowledge of the characteristics of each oral anticoagulant is required at drug cessation and resumption. Unlike warfarin, which has been used in the past five decades, direct oral anticoagulants (DOACs) do not have sensitive indicators such as prothrombin time-international normalized ratio. To avoid major hemorrhages and thromboembolism, quantitative assays can be implemented for DOAC monitoring and for reversal therapies in perioperative settings.

Old and new oral anticoagulants: Food, herbal medicines and drug interactions

The most commonly prescribed oral anticoagulants worldwide are the vitamin K antagonists (VKAs) such as warfarin. Factors affecting the pharmacokinetics of VKAs are important because deviations from their narrow therapeutic window can result in bleedings due to over-anticoagulation or thrombosis because of under-anticoagulation. In addition to pharmacodynamic interactions (e.g., augmented bleeding risk for concomitant use of NSAIDs), interactions with drugs, foods, herbs, and over-the-counter medications may affect the risk/benefit ratio of VKAs. Direct oral anticoagulants (DOACs) including Factor Xa inhibitors (rivaroxaban, apixaban and edoxaban) and thrombin inhibitor (dabigatran) are poised to replace warfarin. Phase-3 studies and real-world evaluations have established that the safety profile of DOACs is superior to those of VKAs. However, some pharmacokinetic and pharmacodynamic interactions are expected. Herein we present a critical review of VKAs and DOACs with focus on their potential for interactions with drugs, foods, herbs and over-the-counter medications.

An update on the pharmaceutical management of thrombosis

INTRODUCTION

Anticoagulants such as heparins and vitamin K antagonists (VKA) are effective for thrombosis prevention and treatment, but are associated with the risk of bleeding and other limitations, spurring the search for improved drugs. Areas covered: to evaluate the newer anticoagulants, focusing on those tested in phase III clinical trials such as direct oral anticoagulants (DOACs), antisense oligonucleotides (ASO) and warfarin analogues. DOACs such as dabigatran, rivaroxaban, apixaban and edoxaban are licensed for stroke prevention in atrial fibrillation and treatment of venous thromboembolism, dabigatran, rivaroxaban and apixaban for postoperative thromboprophylaxis in patients undergoing elective hip or knee arthroplasty and rivaroxaban for secondary prevention of acute coronary syndromes. ASO interfering with Factor XI hepatic synthesis were effective and safe for thromboprophylaxis in elective knee arthroplasty. Expert opinion: DOACs have overcome some limitations of anticoagulants such as VKA, but are still associated with a risk of bleeding and they lack both standardized and widely available tests measuring their anticoagulant effect and a reversal agent, except for idarucizumab, specific for dabigatran, in case of major or life threatening bleeding or emergency surgery. Agents targeting Factor XI and possibly Factor XII may be ideal anticoagulants, as they can prevent thrombosis with low bleeding risk.

Erratum to: Pharmacology of anticoagulants used in the treatment of venous thromboembolism

Anticoagulant drugs are the foundation of therapy for patients with VTE. While effective therapeutic agents, anticoagulants can also result in hemorrhage and other side effects. Thus, anticoagulant therapy selection should be guided by the risks, benefits and pharmacologic characteristics of each agent for each patient. Safe use of anticoagulants requires not only an in-depth knowledge of their pharmacologic properties but also a comprehensive approach to patient management and education. This paper will summarize the key pharmacologic properties of the anticoagulant agents used in the treatment of patients with VTE.

Novel Oral Anticoagulants for Venous Thromboembolism with Special Emphasis on Risk of Hemorrhagic Complications and Reversal Agents

Warfarin was the only oral anticoagulant available for the treatment of venous thromboembolism for about half a century until the recent approval of novel oral agents dabigatran, rivoraxaban and apixaban. This presents new classes of medications less cumbersome to use. They do not require frequent laboratory monitoring or have nurmerous drug interactions. On the other hand it also poses a challenge to the physicians deciding which agent to use in specific patient populations, how to predict the bleeding risk compared to warfarin and between the different novel agents and how to manage bleeding with relatively recent discovery of few potential antidotes. This review summarizes the major trials that led to the approval of these agents and their exclusion criteria helping physicians understand which patient types might not benefit from these agents. It provides clinical pearls invaluable in everyday practice such as transitioning between traditional and novel anticoagulants, dose adjustments for high risk populations, drug interactions and cost analysis. Futhermore, the review provides direct comparisons with warfarin and indirect comparisons among the novel agents in terms of efficacy and bleeding risk narrating the numbers of patients with intracranial, gastrointestinal and fatal hemorrhages in each of the major trials. We hope that this review will help the physicians inform their patients about the benefits and risks of these agents and enable them to make an informed selection of the most appropriate anticoagulant.

The Role of New Oral Anticoagulants (NOACs) in Cancer Patients

New oral anticoagulants (NOACs) are likely to have a major impact in the next few years, changing clinical practice of anticoagulation therapy. Evidence on its efficacy and superiority to vitamin K antagonists (VKAs) in treating non-cancer patients have been reported in a few clinical trials. However, patients with cancer are complicated by the prothrombotic nature of the disease, need for potentially invasive surgery and interventions, and altered drug handling. This chapter examines the available evidence and guidelines on the use of NOAC in patients with cancer.

Pharmacology of anticoagulants used in the treatment of venous thromboembolism

Anticoagulant drugs are the foundation of therapy for patients with VTE. While effective therapeutic agents, anticoagulants can also result in hemorrhage and other side effects. Thus, anticoagulant therapy selection should be guided by the risks, benefits and pharmacologic characteristics of each agent for each patient. Safe use of anticoagulants requires not only an in-depth knowledge of their pharmacologic properties but also a comprehensive approach to patient management and education. This paper will summarize the key pharmacologic properties of the anticoagulant agents used in the treatment of patients with VTE.

Direct oral anticoagulants in the treatment of venous thromboembolism, with a focus on patients with pulmonary embolism: an evidence-based review

Pulmonary embolism (PE) is a relatively common cardiovascular emergency. PE and deep vein thrombosis (DVT) are considered expressions of the same disease, termed as venous thromboembolism (VTE). In the present review, we describe and meta-analyze the efficacy and safety data available with the direct oral anticoagulants (DOAC; dabigatran, rivaroxaban, apixaban, edoxaban) in clinical trials testing these new compounds in the acute/long-term and extended therapy of VTE, providing subgroup analyses in patients with index PE. We analyzed ten studies in 35,019 randomized patients. A total of 14,364 patients (41%) had index PE. In the acute/long-term treatment of VTE, the DOAC showed comparable efficacy in preventing recurrent VTE to standard treatment in patients with index PE (risk ratio [RR]: 0.88; 95% confidence interval [CI]: 0.70–1.11) and index DVT (RR: 0.93; 95% CI: 0.75–1.16) (P for subgroup differences =0.76). VTE recurrence depending on PE anatomical extension and presence/absence of right ventricular dysfunction was only reported in two trials, with results being consistent with those obtained in the overall study populations. In the single trial comparing extended therapy of VTE with DOAC versus warfarin, the point estimate for recurrent VTE tended to disfavor the DOAC in patients with index PE (RR: 2.05; 95% CI: 0.83–5.03) and in patients with index DVT (RR: 1.11; 95% CI: 0.49–2.50) (P for subgroup differences =0.32). In trials that compared DOAC versus placebo for extended therapy, the reduction in recurrent VTE was consistent in patients with PE (RR: 0.15; 95% CI: 0.01–1.82) and in patients with DVT (RR: 0.25; 95% CI: 0.10–0.61) (P for subgroup differences =0.71). The DOAC were associated with a consistently lower risk of clinically relevant bleeding (CRB) than standard treatment of acute VTE and higher risk of CRB than placebo for extended therapy of VTE regardless of index event. In summary, the DOAC were as effective as, and safer than, standard treatment of (hemodynamically stable) PE. Their efficacy in preventing recurrent VTE seemed consistent regardless of anatomical extension of PE (extensive, intermediate, or limit) or presence/absence of right ventricular dysfunction although the data are limited. For extended therapy, the DOAC were more effective than placebo in preventing recurrent VTE but were associated with an increase in CRB regardless of index event.

Potential use of NOACs in developing countries: pros and cons

PURPOSE

Although vitamin K antagonists (VKAs) are effective for long-term thromboprophylaxis in atrial fibrillation (AF), their limitations have led to widespread underutilisation, especially in the developing world. Novel oral anticoagulants (NOACs) have emerged as promising alternatives to VKAs, although there are some particular considerations and challenges to their introduction in developing countries. This review summarises the current state of antithrombotic management of AF in the developing world, explores the early evidence for the NOACs and describes some of the special considerations that must be taken into account when considering the role of the NOACs within developing countries' health care systems.

METHODS

A literature search was conducted via PubMed and Google Scholar to find articles published in English between the years 2000 to 2014. Search terms used were "atrial fibrillation", "oral anticoagulants", "warfarin", "NOACs", "dabigatran", "rivaroxaban", "apixaban", "edoxaban", "time in therapeutic range", "International Normalized Ratio" "cost-effectiveness", "stroke", "adverse-drug reactions" and "drug-drug interactions", together with the individual names of developing countries as listed by the World Bank. We reviewed the results of randomized clinical trials, relevant retrospective and prospective studies, case-studies and review articles.

RESULTS

Many developing countries lack or have sporadic data on the quality of AF management, making it difficult to anticipate the potential impact of NOACs in these settings. The utilisation of anticoagulants for AF appears highly variable in developing countries. Given the issues associated with VKA therapy in many developing countries, NOACs offer some potential advantages; however, there is insufficient evidence to advocate the widespread replacement of warfarin at present. VKAs may continue to have a role in selected patients or countries, especially if alternative monitoring strategies can be utilised.

CONCLUSION

The evaluation of the introduction of NOACs should consider safety, budget concerns and the quality of oral anticoagulation care achieved by each country. Prospective registries will be important in developing countries to better elucidate the comparative safety, efficacy and cost-effectiveness of NOACs and VKAs as NOACs are introduced into practice.

Discovery of glycyrrhetinic acid as an orally active, direct inhibitor of blood coagulation factor xa

INTRODUCTION

Factor Xa (FXa) plays an important role in blood coagulation. This study investigated glycyrrhetinic acid, a small molecule derived from Chinese herbs, and whether it has a direct inhibitory effect on FXa to display its anticoagulant activity.

MATERIALS AND METHODS

Enzyme activities of FXa, plasmin, trypsin and thrombin, inhibition of FXa enzyme kinetics and plasma clotting time by glycyrrhentinic acid were performed in vitro. A rat tail-bleeding model and a rat venous stasis model were also used to evaluate in vivo tail-bleeding time and thrombus formation, respectively.

RESULTS

Glycyrrhetinic acid in vitro directly inhibited FXa uncompetitivly with IC50 of 32.6 ± 1.24 μmol/L, and displayed 2-, 14- and 20-fold selectivity for FXa when compared to plasmin, thrombin and trypsin, respectively. The plasma clotting time was increased in a dose-dependent manner. The prothrombin time doubled (PT2), when the concentration of glycyrrhetinic acid reached 2.02 mmol/L. During in vivo experiments intragastric administration of glycyrrhetinic acid caused a dose-dependent reduction in thrombus weight on the rat venous stasis model (all P<0.05). 50 mg/kg glycyrrhetinic acid resulted in 34.8% of venous thrombus weight lost, compared to the control. In addition, 200, 300 and 400 mg/kg doses of glycyrrhetinic acid caused a moderate hemorrhagic effect in the rat tail-bleeding model by prolonging bleeding time 1.1-, 1.5- and 1.9-fold compared to the control, respectively.

CONCLUSIONS

Glycyrrhetinic acid is a direct inhibitor of FXa that is effective by oral administration, and with further research could be used to treat blood coagulation disorders.