Direct Oral Anticoagulants in Patients With Atrial Fibrillation and Advanced Liver Disease: An Exploratory Meta-Analysis

Molecular Mechanisms Underlying Vascular Liver Diseases: Focus on Thrombosis

Vascular liver disorders (VLDs) comprise a wide spectrum of clinical-pathological entities that primarily affect the hepatic vascular system of both cirrhotic and non-cirrhotic patients. VLDs more frequently involve the portal and the hepatic veins, as well as liver sinusoids, resulting in an imbalance of liver homeostasis with serious consequences, such as the development of portal hypertension and liver fibrosis. Surprisingly, many VLDs are characterized by a prothrombotic phenotype. The molecular mechanisms that cause thrombosis in VLD are only partially explained by the alteration in the Virchow's triad (hypercoagulability, blood stasis, and endothelial damage) and nowadays their pathogenesis is incompletely described and understood. Studies about this topic have been hampered by the low incidence of VLDs in the general population and by the absence of suitable animal models. Recently, the role of coagulation imbalance in liver disease has been postulated as one of the main mechanisms linked to fibrogenesis, so a novel interest in vascular alterations of the liver has been renewed. This review provides a detailed analysis of the current knowledge of molecular mechanisms of VLD. We also focus on the promising role of anticoagulation as a strategy to prevent liver complications and to improve the outcome of these patients.

Anticoagulation improves survival in patients with cirrhosis and portal vein thrombosis: The IMPORTAL competing-risk meta-analysis

BACKGROUND & AIMS

Previous meta-analyses demonstrated the safety and efficacy of anticoagulation in the recanalization of portal vein thrombosis in patients with cirrhosis. Whether this benefit translates into improved survival is unknown. We conducted an individual patient data (IPD) meta-analysis to assess the effect of anticoagulation on all-cause mortality in patients with cirrhosis and portal vein thrombosis.

METHODS

In this IPD meta-analysis, we selected studies comparing anticoagulation vs. no treatment in patients with cirrhosis and portal vein thrombosis from PubMed, Embase, and Cochrane databases (until June 2020) (PROSPERO no.: CRD42020140026). IPD were subsequently requested from authors. The primary outcome - the effect of anticoagulation on all-cause mortality - was assessed by a one-step meta-analysis based on a competing-risk model with liver transplantation as the competing event. The model was adjusted for clinically relevant confounders. A multilevel mixed-effects logistic regression model was used to determine the effect of anticoagulation on recanalization.

RESULTS

Individual data on 500 patients from five studies were included; 205 (41%) received anticoagulation and 295 did not. Anticoagulation reduced all-cause mortality (adjusted subdistribution hazard ratio 0.59; 95% CI 0.49-0.70), independently of thrombosis severity and recanalization. The effect of anticoagulation on all-cause mortality was consistent with a reduction in liver-related mortality. The recanalization rate was higher in the anticoagulation arm (adjusted odds ratio 3.45; 95% CI 2.22-5.36). The non-portal-hypertension-related bleeding rate was significantly greater in the anticoagulation group.

CONCLUSIONS

Anticoagulation reduces all-cause mortality in patients with cirrhosis and portal vein thrombosis independently of recanalization, but at the expense of increasing non-portal hypertension-related bleeding.

PROSPERO REGISTRATION NUMBER

CRD42020140026.

IMPACT AND IMPLICATIONS

Anticoagulation is effective in promoting recanalization of portal vein thrombosis in patients with cirrhosis, but whether this benefit translates into improved survival is controversial. Our individual patient data meta-analysis based on a competing-risk model with liver transplantation as the competing event shows that anticoagulation reduces all-cause mortality in patients with cirrhosis and portal vein thrombosis independently of recanalization. According to our findings, portal vein thrombosis may identify a group of patients with cirrhosis that benefit from long-term anticoagulation.

Improving Management of Portal Hypertension: The Potential Benefit of Non-Etiological Therapies in Cirrhosis

Portal hypertension is the consequence of cirrhosis and results from increased sinusoidal vascular resistance and hepatic blood inflow. Etiological therapies represent the first intervention to prevent a significant increase in portal pressure due to chronic liver damage. However, other superimposed pathophysiological drivers may worsen liver disease, including inflammation, bacterial translocation, endothelial dysfunction, and hyperactivation of hemostasis. These mechanisms can be targeted by a specific class of drugs already used in clinical practice. Albumin, rifaximin, statins, aspirin, and anticoagulants have been tested in cirrhosis and were a topic of discussion in the last Baveno consensus as non-etiological therapies. Based on the pathogenesis of portal hypertension in cirrhosis, our review summarizes the main mechanisms targeted by these drugs as well as the clinical evidence that considers them a valid complementary option to manage patients with cirrhosis and portal hypertension.

Risk and Management of Bleeding Complications with Direct Oral Anticoagulants in Patients with Atrial Fibrillation and Venous Thromboembolism: a Narrative Review

Atrial fibrillation (AF) and venous thromboembolism (VTE) are highly prevalent conditions with a significant healthcare burden, and represent the main indications for anticoagulation. Direct oral anticoagulants (DOACs) are the first choice treatment of AF/VTE, and have become the most prescribed class of anticoagulants globally, overtaking vitamin K antagonists (VKAs). Compared to VKAs, DOACs have a similar or better efficacy/safety profile, with reduced risk of intracerebral hemorrhage (ICH), while the risk of major bleeding and other bleeding harms may vary depending on the type of DOAC. We have critically reviewed available evidence from randomized controlled trials and observational studies regarding the risk of bleeding complications of DOACs compared to VKAs in patients with AF and VTE. Special patient populations (e.g., elderly, extreme body weights, chronic kidney disease) have specifically been addressed. Management of bleeding complications and possible resumption of anticoagulation, in particular after ICH and gastrointestinal bleeding, are also discussed. Finally, some suggestions are provided to choose the optimal DOAC to minimize adverse events according to individual patient characteristics and bleeding risk.

Thromboembolism and bleeding in patients with atrial fibrillation and liver disease - A nationwide register-based cohort study: Thromboembolism and bleeding in liver disease

BACKGROUND

Balancing the risk of thromboembolism and bleeding in patients with liver disease and atrial fibrillation/flutter is particularly challenging.

PURPOSE

To examine the risks of thromboembolism and bleeding with use/non-use of oral anticoagulation (including vitamin K-antagonists and direct oral anticoagulants) in patients with liver disease and AF.

METHODS

Danish nationwide register-based cohort study of anticoagulant naive individuals with liver disease, incident atrial fibrillation/flutter, and a CHA₂DS₂-VASc-score≥1 (men) or ≥2 (women), alive 30 days after atrial fibrillation/flutter diagnosis. Thromboembolism was a composite of ischaemic stroke, transient ischaemic attack, or venous thromboembolism. Bleeding was a composite of gastrointestinal, intracerebral, or urogenital bleeding requiring hospitalisation, or epistaxis requiring emergency department visit or hospital admission. Cause-specific Cox-regression was used to estimate absolute risks and average risk ratios standardised to covariate distributions. Because of significant interactions with anticoagulants, results for thromboembolism were stratified for CHA2DS2-VASc-score, and results for bleeding were stratified for cirrhotic/non-cirrhotic liver disease.

RESULTS

Four hundred and nine of 1,238 patients with liver disease and new atrial fibrillation/flutter initiated anticoagulants. Amongst patients with a CHA2DS2-VASc-score of 1-2 (2-3 for women), five-year thromboembolism incidence rates were low and similar in the anticoagulant (6.5%) versus no anticoagulant (5.5%) groups (average risk ratio 1.19 [95%CI, 0.22-2.16]). In patients with a CHA2DS2-VASc-score>2 (>3 for women), incidence rates were 16% versus 24% (average risk ratio 0.66 [95%CI, 0.45-0.87]). Bleeding risks appeared higher amongst patients with cirrhotic versus non-cirrhotic disease but were not significantly affected by anticoagulant status.

CONCLUSION

Oral anticoagulant initiation in patients with liver disease, incident new atrial fibrillation/flutter, and a high CHA2DS2-VASc-score was associated with a reduced thromboembolism risk. Bleeding risk was not increased with anticoagulation, irrespective of the type of liver disease.

Antiplatelet Medications Are Associated With Bleeding and Decompensation Events Among Patients With Cirrhosis

BACKGROUND

In an aging population with cardiovascular comorbidities, anticoagulant (AC), antiplatelet (AP), and nonsteroidal anti-inflammatory drug (NSAID) use are increasing. It remains unclear whether these agents pose increased bleeding risk in cirrhosis. This study aimed to assess the association between these medications and bleeding and portal hypertension complications in cirrhosis.

METHODS

The IMS PharMetrics database was used to identify privately insured adults diagnosed with cirrhosis from 2007 to 2015, stratified as compensated or decompensated based on the presence of portal hypertensive complications 1 year before cirrhosis diagnosis. Bleeding or decompensation outcomes were assessed 6 to 18 months after cirrhosis diagnosis using a landmark analysis design. Multivariable Cox proportional hazards regression modeling assessed associations between AC, AP, and NSAID drug exposures and outcomes adjusting for covariates.

RESULTS

A total of 18,070 cirrhosis patients were analyzed; 57% male; 74% ages 50 to 64 years; 34% with a prior decompensation. Overall, 377 (2%) had claims for ACs; 385 (2%) APs; and 1231 (7%) NSAIDs. APs were associated with increased bleeding [adjusted hazard ratio (aHR)=1.31; 95% confidence interval (CI): 1.00, 1.72] and decompensation events (aHR=1.44; 95% CI: 1.06, 1.95) in a 9-month landmark analysis. NSAIDs were significantly associated with bleeding events (aHR=1.29; 95% CI: 1.06, 1.57) on 3-month landmark analysis. No statistically significant associations were seen between ACs and bleeding or decompensation outcomes in adjusted analyses.

CONCLUSIONS

AP use was associated with increased bleeding and decompensation events among privately insured patients with cirrhosis. NSAID use was associated with significant early bleeding, but not decompensations. Lastly ACs were not associated with bleeding or decompensation outcomes.

Haemostatic alterations and management of haemostasis in patients with cirrhosis

Patients with cirrhosis frequently acquire complex changes in their haemostatic system including a decreased platelet count and decreased levels of various haemostatic proteins. Although historically patients with cirrhosis were thought to have a haemostasis-related bleeding tendency, it is now widely accepted that the haemostatic system of patients with cirrhosis remains in balance as a result of simultaneous changes in pro- and anti-haemostatic systems. The concept of rebalanced haemostasis has led to changes in clinical management, although firm evidence from well-designed clinical studies is largely lacking. For example, many invasive procedures in patients with cirrhosis and a prolonged prothrombin time are now performed without prophylaxis with fresh frozen plasma. Conversely, clinicians have become more aware of the need for anti-thrombotic therapy, even in those patients with abnormal routine coagulation tests. This paper will outline recent advances in pathogenesis, prevention and treatment of both bleeding and thrombotic complications in patients with cirrhosis. Among other topics, we will discuss the haemostatic status of acutely ill patients with cirrhosis, the various causes of bleeding in patients with cirrhosis, and how best to prevent or treat bleeding. In addition, we will discuss the hypercoagulable features of patients with cirrhosis, new insights into the pathogenesis of portal vein thrombosis, and how best to prevent or treat thromboses.

Efficacy and safety of direct oral anticoagulants versus vitamin K antagonist for portal vein thrombosis in cirrhosis: A systematic review and meta-analysis

INTRODUCTION AND AIM

Portal vein thrombosis (PVT) is associated with a higher risk of liver-related complications. Recent guidelines recommend direct-acting anticoagulants (DOAC) in patients with cirrhosis and non-tumoral PVT. However, data on the efficacy and safety of DOAC in these patients remain limited. We aim to investigate the efficacy and safety of DOAC compared to vitamin K antagonists (VKA) to treat non-tumoral PVT in patients with cirrhosis.

METHODS

We performed a systematic search of six electronic databases using MeSH term and free text. We selected all studies comparing the use of DOACs with vitamin K antagonist to treat PVT in cirrhosis. The primary outcome was PVT recanalization. Secondary outcomes were and PVT progression, major bleeding, variceal bleeding and death.

RESULTS

From 944 citations, we included 552 subjects from a total of 11 studies (10 observational and 1 randomized trial) that fulfilled the inclusion criteria. We found that DOAC were associated with a higher pooled rate of PVT recanalization (RR = 1.67, 95%CI: 1.02, 2.74, I² = 79%) and lower pooled risk of PVT progression (RR = 0.14, 95%CI: 0.03-0.57, I² = 0%). The pooled risk of major bleeding (RR = 0.29, 95%CI: 0.08-1.01, I² = 0%), variceal bleeding (RR = 1.29, 95%CI: 0.64-2.59, I² = 0%) and death (RR = 0.31, 95%CI: 0.01-9.578, I² = 80%) was similar between DOAC and VKA.

CONCLUSION

For the treatment of PVT in patients with cirrhosis, the bleeding risk was comparable between DOAC and VKA. However, DOAC were associated with a higher pooled rate of PVT recanalization. Dedicated randomized studies are needed to confirm these findings.

Antithrombotic therapy in patients with liver disease: population-based insights on variations in prescribing trends, adherence, persistence and impact on stroke and bleeding

BACKGROUND

Patients with liver disease have complex haemostasis and due to such contraindications, landmark randomised controlled trials investigating antithrombotic medicines have often excluded these patients. As a result, there has been limited consensus on the safety, efficacy and monitoring practices of anticoagulant and antiplatelet therapy in patients with liver disease. This study aims to investigate prescribing prevalence, adherence, persistence and impact of adherence on bleeding and stroke risk in people with and without liver disease taking anticoagulants and antiplatelets.

METHODS

We employed a population-based cohort consisting of person-level linked records from primary care, secondary care and the death registry. The cohort consisted of 3,929,596 adults aged ≥ 30 years during the study period of 1998 to 2020 and registered with an NHS general practitioner in England. The primary outcome was prescribing prevalence, adherence to and persistence with anticoagulant and antiplatelet therapy comparing patients with and without liver disease. Risk factors for non-adherence and non-persistence were analysed using multivariable logistic regression and Cox regression. Impact of adherence on bleeding and ischaemic stroke was assessed.

FINDINGS

Among patients with any of the six liver diseases (ALD, autoimmune liver disease, cirrhosis, HBV, HCV and NAFLD), we identified 4,237 individuals with incident atrial fibrillation (indication for anticoagulants) and 4,929 individuals with incident myocardial infarction, transient ischaemic attack, unstable angina or peripheral arterial disease (indication for antiplatelets). Among patients without liver disease, 321,510 and 386,643 individuals were identified as having indications for anticoagulant and antiplatelet therapy, respectively. Among drug-naïve individuals, prescribing prevalence was lower in patients with liver disease compared with individuals without liver disease: anticoagulants (20.6% [806/3,921] vs. 33.5% [103,222/307,877]) and antiplatelets (56.2% [2,207/3,927] vs. 71.1% [249,258/350,803]). Primary non-adherence rates (stopping after one prescription) were higher in patients with liver disease, compared with those without liver disease: anticoagulants (7.9% [64/806] vs. 4.7% [4,841/103,222]) and antiplatelets (6.2% [137/2,207] vs. 4.4% [10,993/249,258]). Among individuals who were not primary non-adherent and had at least 12 months of follow-up, patients with liver disease however had a higher one-year adherence rate: anticoagulants (33.1% [208/628] vs. 29.4% [26,615/90,569]) and antiplatelets (40.9% [743/1,818] vs. 34.4% [76,834/223,154]). Likelihood of non-adherence was lower in apixaban and rivaroxaban (relative to warfarin) and lower in clopidogrel (relative to aspirin). Increased comorbidity burden (by CHA₂DS₂VASc score) was associated with decreased risk of non-adherence and non-persistence with anticoagulants. Overall rates of 'non-adherent, non-persistent' were highest in warfarin (compared with apixaban and rivaroxaban) and aspirin (compared with clopidogrel or dipyridamole) in patients with and without liver disease. Among patients without liver disease, not taking antithrombotic medications for >3 months was associated with a higher risk of stroke, however, adherence to these medications was also associated with a small increase in risk of bleeding. Patients with liver disease (when compared with those without liver disease) had higher risks of stroke, especially when they stopped taking antiplatelets for >3 months. Patients with liver disease who were adherent to antiplatelets, however, had a higher risk of bleeding compared with patients without liver disease.

INTERPRETATION

Use of antithrombotic medicines in patients with and without liver disease is suboptimal with heterogeneity across medicines. As patients with liver disease are excluded from major randomised trials for these drugs, our results provide real-world evidence that may inform medicine optimisation strategies. We outline challenges and opportunities for tackling non-adherence, which begins with understanding patients' views of medicines to help them make informed decisions about appropriate use.

FUNDING

AGL is supported by funding from the Wellcome Trust (204841/Z/16/Z), National Institute for Health Research (NIHR) University College London Hospitals Biomedical Research Centre (BRC714/HI/RW/101440), NIHR Great Ormond Street Hospital Biomedical Research Centre (19RX02), the Health Data Research UK Better Care Catalyst Award (CFC0125) and the Academy of Medical Sciences (SBF006\1084). The funders have no role in the writing of the manuscript or the decision to submit it for publication.

Is antivitamin K reversal required in patients with cirrhosis undergoing liver transplantation?

BACKGROUND

Antivitamin K agent (AVK) reversal in patients with cirrhosis awaiting liver transplantation (LT) is not defined in guidelines. We investigated the effect of reversion with prothrombin complex concentrate (PCC) on intraoperative transfusion, bleeding, and safety in LT patients on AVK.

STUDY DESIGN AND METHODS

In 511 patients undergoing LT, we identified 25 patients treated with AVK (AVK group) and 13 patients with incidental portal vein thrombosis (PVT) without AVK (incidental PVT group). Fifty patients who underwent LT without PVT or AVK matched by age, model for end stage of liver disease (MELD), body mass index (BMI), and cirrhosis etiology were selected as the control group.

RESULTS

There were no significant differences between the three groups in intraoperative blood loss, transfusion, and postoperative bleeding. In the AVK group, there were no differences between patients who received PCC and those who did not in intraoperative blood loss, red blood cells, fibrinogen, and platelet transfusion, or postoperative bleeding. PCC use had no effect on RBC transfusion in patients who had international normalized ratio or clotting time above versus below median values of the two parameters at baseline (2.3 and 103 s, respectively). No thrombotic events were detected in patients who received PCC.

DISCUSSION

These data suggest that systematic administration of PCC to revert AVK prior to LT should be reconsidered.

Direct oral anticoagulant use in special populations

PURPOSE OF REVIEW

The pivotal phase III trials demonstrating efficacy and safety of direct oral anticoagulants (DOACs) in the treatment of venous thromboembolism (VTE) or nonvalvular atrial fibrillation (NVAF) excluded patients with important and common comorbidities, including obesity, advanced chronic kidney disease, cirrhosis, cancer and antiphospholipid antibody syndrome. Despite the lack of large prospective randomized control trials in these patient populations, the use of DOACs has led to a wealth of efficacy and safety data within these groups.

RECENT FINDINGS

Retrospective studies, meta-analyses, national databases and pharmacokinetic data have shed light on the efficacy and safety of DOACs in these patient populations. Although DOACs should be avoided in those with high-risk triple positive antiphospholipid antibody syndrome, advanced cirrhosis, advanced kidney disease and intact gastrointestinal cancers, and used with caution in genitourinary cancers, their use extends beyond the inclusion criteria of the initial randomized control trials.

SUMMARY

DOACs have revolutionized anticoagulant management and have become the cornerstone for VTE treatment and stroke prevention in NVAF. The decision to use DOACs must be individualized. Patient preference, underlying comorbidities and informed consent must always be considered when selecting the most appropriate anticoagulant.

Safety of direct oral anticoagulants in patients with mild to moderate cirrhosis: a systematic review and meta-analysis

To evaluate major bleeding in cirrhosis with use of traditional anticoagulation or direct oral anticoagulants (DOACs), using a standardized definition. Anticoagulation in patients with cirrhosis is often a clinical conundrum for providers as the necessary balance between thrombotic and bleeding risk is complicated by end organ damage. Recent meta-analyses have sought to evaluate the safety and efficacy of direct oral anticoagulants in patients with liver disease. These recent analyses are limited by various bleeding definitions, broad inclusion criteria, and few indications for anticoagulation. We sought to conduct a meta-analysis using a validated definition for major bleeding and compare rates between traditional anticoagulation and DOACs in patients with cirrhosis. Articles were eligible for inclusion if the international society on thrombosis and hemostasis (ISTH) definition of a major bleed was the primary safety outcome. Additionally, only articles including patients with cirrhosis and receiving treatment with anticoagulation for an indication for stroke prevention or venous thromboembolism were eligible. Eligible articles needed a DOAC comparator group against traditional anticoagulant medication. Seven studies met inclusion criteria and compiled data for 683 patients in the meta-analysis. Pooled trial analysis demonstrated no statistically significant difference in the primary outcome of ISTH major bleeding (OR 0.55, 95%CI 0.28-1.07, I² 0%). Individual secondary outcomes of all bleeding, intracerebral hemorrhage, or gastrointestinal bleeding also demonstrated no significant difference between DOACs and traditional anticoagulation. Use of DOACs in patients with mild to moderate cirrhosis carries similar risk to use of traditional anticoagulation.

Direct oral anticoagulants and advanced liver disease: A systematic review and meta-analysis

BACKGROUND

Direct oral anticoagulants (DOACs) are recommended for stroke prevention in patients with atrial fibrillation (AF) or for treatment of deep vein thrombosis, although some concerns about safety and efficacy were raised on the use of these drugs in patients with advanced liver disease (ALD). We want to investigate the association of DOACs use with the bleeding and ischaemic risk.

MATERIAL AND METHODS

We performed a systematic review and metanalysis of clinical studies retrieved from PubMed (via MEDLINE) and Cochrane (CENTRAL) databases addressing the impact of DOACs therapy on bleeding events including intracranial haemorrhage (ICH), gastrointestinal and major bleeding. Secondary end points were all-cause death, ischaemic stroke/systemic embolism (IS/SE) and recurrence/progression of vein thrombosis (rDVT).

RESULTS

12 studies were included in the meta-analysis: a total of 43 532 patients with ALD or cirrhosis, of whom 27 574 (63.3%) were on treatment with DOACs and 15 958 were in warfarin/low molecular weight heparin. DOACs reduced the incidence of major bleeding by 61% (pooled Hazard Ratio [HR] 0.39, 95% Confidence Interval [CI] 0.21-0.70), ICH by 52% (HR 0.48, 95% CI 0.40-0.59), while no difference in the reduction of any and gastrointestinal bleeding were observed. DOACs reduced also rDVT by 82% (HR 0.18, 95%CI 0.06-0.57), but did not reduce death and IS/SE. No difference was shown according to oesophageal varices and Child Pugh score in the meta-regression analysis between warfarin/heparin and DOACs performed on each outcome.

CONCLUSIONS

DOACs are associated with a lower incidence of bleeding and may be an attractive therapeutic option in patients with cirrhosis.

Anticoagulation in patients with advanced liver disease: an open issue

Liver disease has been long considered as a risk factor for bleeding for the presence of prolongation of global tests of clotting activation and low platelet count. For this reason, the use of anticoagulants in patients with liver disease and an indication to anticoagulation, such as atrial fibrillation of venous thrombosis, has been poorly considered. Furthermore, recent studies underscored the fact that patients with chronic liver disease may experience thrombosis in portal as well as systemic circulation and treatment with anticoagulants should be considered. The introduction of direct oral anticoagulants has increased therapeutic options for thromboprophylaxis; however, evidence on their safety and efficacy in specific populations, such as patients with liver disease, is still scarce and needs further investigation. Thus, atrial fibrillation patients with coexistent liver disease have been excluded from clinical trials with direct oral anticoagulants. Here, we provide an overview on mechanisms of thrombosis in patients with advanced chronic liver disease and a summary of evidence on the use of oral anticoagulants in patients with liver disease and portal vein thrombosis or atrial fibrillation.

Direct oral anticoagulants: evidence and unresolved issues

Currently licenced direct oral anticoagulants selectively target thrombin (eg, dabigatran) or coagulation factor Xa (eg, apixaban, betrixaban, edoxaban, and rivaroxaban). Designed to be given in fixed doses without routine monitoring, direct oral anticoagulants have a lower propensity for food and drug interactions than do vitamin K antagonists, and in randomised controlled trials involving around 250 000 patients, they were at least as effective for prevention and treatment of thrombosis and were associated with a lower risk of life-threatening bleeding. The absolute benefits of direct oral anticoagulants over vitamin K antagonists are modest; however, guidelines recommend them in preference to vitamin K antagonists for most indications because of their ease of use and superior safety. The greatest benefits of direct oral anticoagulants are likely to be in patients who were previously deemed unsuitable for vitamin K antagonist therapy. The emergence of generic preparations is expected to further increase the uptake of direct oral anticoagulants, particularly in countries where they are currently not widely used because of cost. Direct oral anticoagulants are contraindicated in patients with mechanical heart valves and should be used with caution or avoided in patients with advanced kidney or liver disease. In this Therapeutics paper, we review the pharmacology of direct oral anticoagulants, summarise the evidence that led to their approval and incorporation into treatment guidelines, and explore key unresolved issues. We also briefly discuss future perspectives for the development of oral anticoagulants.