Use of direct-acting oral anticoagulants in solid organ transplantation: A systematic review

The use of direct-acting oral anticoagulants (DOACs) has increased secondary to the mounting evidence for comparable efficacy and potentially superior safety to vitamin K antagonists (VKAs) in the general population. However, insufficient data regarding DOAC use in solid organ transplant (SOT) recipients and numerous pharmacokinetic and pharmacodynamic considerations limit their use in this highly selected patient population. A systematic review of recent clinical evidence on the safety and efficacy of DOACs compared to VKAs in SOT recipients was conducted. Additional considerations including transplant-specific strategies for DOAC reversal and common pharmacokinetic/pharmacodynamic concerns were also reviewed. Although current evidence is limited to single-center retrospective analyses, DOACs, especially apixaban, appear to be a safe and effective alternative to VKAs for SOT recipients with stable graft function and without drug-drug interactions. Reliable data on DOAC reversal at the time of transplant surgery are lacking, and clinicians should consider idarucizumab, andexanet alfa, and other non-specific reversal agents on an individual patient basis. There is no evidence supporting deviations from the Food and Drug Administration labeling recommendations for DOAC dosing in the setting of drug-drug interactions, obesity, and renal function, especially in patients on hemodialysis.     

Switching of Oral Anticoagulation Therapy After PCI in Patients With Atrial Fibrillation: The RE-DUAL PCI Trial Subanalysis

ObjectivesThe aim of this study was to assess if prior oral anticoagulant agent (OAC) use modifies the lower bleeding risk observed with dabigatran dual therapy (dabigatran twice daily plus a P2Y₁₂ inhibitor) versus warfarin triple therapy (warfarin plus a P2Y₁₂ inhibitor plus aspirin) in patients with atrial fibrillation who underwent percutaneous coronary intervention (PCI).BackgroundIn the RE-DUAL PCI (Randomized Evaluation of Dual Antithrombotic Therapy With Dabigatran Versus Triple Therapy With Warfarin in Patients With Nonvalvular Atrial Fibrillation Undergoing Percutaneous Coronary Intervention) trial, the primary outcome of major bleeding or clinically relevant nonmajor bleeding was lower with dabigatran dual therapy versus warfarin triple therapy in patients with atrial fibrillation who underwent PCI.MethodsA total of 2,725 patients were randomized to dual therapy with dabigatran (110 or 150 mg twice daily) plus clopidogrel or ticagrelor or triple therapy with warfarin plus aspirin and clopidogrel or ticagrelor. Subgroup analysis compared risk for major bleeding or clinically relevant nonmajor bleeding and a composite thromboembolic endpoint in patients with prior OAC use and in those who were OAC treatment naive.ResultsRisk for major bleeding or clinically relevant nonmajor bleeding was reduced with both dabigatran dual therapies compared with warfarin triple therapy in both the prior OAC use group (hazard ratios: 0.58 [95% confidence interval (CI): 0.42 to 0.81] and 0.61 [95% CI: 0.41 to 0.92] with 110 and 150 mg dabigatran, respectively) and the OAC-naive group (hazard ratios: 0.49 [95% CI: 0.38 to 0.63] and 0.76 [95% CI: 0.59 to 0.97] with 110 and 150 mg dabigatran) (p for interaction = 0.42 and 0.37, 110 and 150 mg dabigatran, respectively). The risk for thromboembolic events seemed similar with dabigatran dual therapy (both doses) and warfarin triple therapy across subgroups.ConclusionsBleeding risk was reduced with dabigatran dual therapy versus warfarin triple therapy in patients with atrial fibrillation after PCI, regardless of whether they were prior OAC users or OAC treatment naive. These results suggest that it is also safe to switch patients on OAC pre-PCI to dabigatran dual therapy post-PCI.     

Dabigatran etexilate for thromboembolic prophylaxis in non-valvular atrial fibrillation: the RE-LY study and substudies with commentary

In 2010, dabigatran etexilate, a direct thrombin inhibitor, was the first new oral anticoagulant to be approved for thromboembolic prophylaxis in atrial fibrillation in over 50 years. Dabigatran, unlike warfarin, has a short half-life with a rapid onset of anticoagulant effect, does not require dose adjustment or monitoring, and does not interact with food. The RE-LY trial compared two doses of dabigatran (110 and 150 mg twice daily) with adjusted dose warfarin in patients with non-valvular atrial fibrillation and at least 1 stroke risk factor. Compared with warfarin, dabigatran 150 mg twice daily was superior in reducing the risk of stroke or systemic embolism and was associated with a similar rate of major bleeding, while dabigatran 110 mg twice daily was equally effective in reducing stroke or systemic embolism and was associated with less major bleeding. Despite these favorable results, there remains disagreement regarding the optimal dose and overall safety of dabigatran in certain patient populations including the elderly and those with renal dysfunction.     

New therapeutic option for thromboembolism – dabigatran etexilate

Background: Thrombin plays a key role in blood coagulation and haemostasis; thus its inhibition has been identified as a reasonable target to block the coagulation cascade. Direct thrombin inhibitors are potential prophylactic agents for venous thromboembolism and arterial thrombosis, which often accompany operative procedures and cardiac disease, especially orthopedic surgery and atrial fibrillation, respectively. New orally available anticoagulant agents with a wide therapeutic window are keenly anticipated because warfarin and heparins have some disadvantages, and recent progress in pharmaceutical techniques has led to the development of orally administered direct thrombin inhibitors. Objectives: In this review, we discuss the usefulness of dabigatran etexilate as a new therapeutic option for preventing thromboembolism, including chemistry, pharmacokinetics, and pharmacodynamics, from the results of recent clinical studies. Methods: We systematically focused on relevant published studies, as data from recent clinical studies were difficult to obtain owing to their ongoing status. Conclusions: Dabigatran etexilate is a promising new oral anticoagulant that offers greatly expanded therapeutic options for both patients and physicians.     

The pharmacokinetics, pharmacodynamics and tolerability of dabigatran etexilate, a new oral direct thrombin inhibitor, in healthy male subjects

AIMS: The novel direct thrombin inhibitor (DTI), dabigatran etexilate (Boehringer Ingelheim Pharma GmbH & Co. KG), shows potential as an oral antithrombotic agent. Two double-blind, randomized trials were undertaken to investigate the pharmacokinetics (PK), pharmacodynamics (PD) and tolerability of orally administered dabigatran etexilate in healthy male subjects. METHODS: Dabigatran etexilate or placebo was administered orally at single doses of 10-400 mg (n = 40) or at multiple doses of 50-400 mg three times daily for 6 days (n = 40). Plasma and urine samples were collected over time to determine the PK profile of dabigatran. PD activity was assessed by its effects on blood coagulation parameters: activated partial thromboplastin time (aPTT), prothrombin time (PT), reported as international normalized ratio (INR), thrombin time (TT), and ecarin clotting time (ECT). All adverse events were recorded. RESULTS: Dabigatran etexilate was rapidly absorbed with peak plasma concentrations of dabigatran reached within 2 h of administration. This was followed by a rapid distribution/elimination phase and a terminal phase, with associated estimated half-lives of 8-10 h and 14-17 h with single and multiple dose administrations, respectively. Dabigatran exhibited linear PK characteristics with dose-proportional increases observed in maximum plasma concentration and area under the curve. Steady-state conditions were reached within 3 days with multiple dosing. The mean apparent volume of distribution during the terminal phase (V(z)/F) of 1860 l (range 1430-2400 l) and the apparent total clearance after oral administration (CL(tot)/F) of 2031 ml min(-1) (range 1480-2430), were dose independent. Time curves for aPTT, INR, TT and ECT paralleled plasma concentration-time curves with values increasing rapidly and in a dose-dependent manner. At the highest dose of 400 mg administered three times daily, maximum prolongations over baseline of 3.1 (aPTT), 3.5 (INR), 29 (TT) and 9.5-fold (ECT) were observed. Dabigatran underwent conjugation with glucuronic acid to form pharmacologically active conjugates that accounted for approximately 20% of total dabigatran in plasma. Overall, variability in PK parameters was low to moderate, with an average interindividual coefficient of variation (CV) of approximately 30% and variability in PD parameters was low, with CV < 10%. Of the four assays, TT and ECT exhibited the greatest sensitivity and precision within the anticipated therapeutic dose range. Bleeding events were few and were mild-to-moderate in intensity, occurring only in the higher, multiple dose groups. CONCLUSIONS: These data suggest that dabigatran etexilate is a promising novel oral DTI with predictable PK and PD characteristics and good tolerability. Further investigation of dabigatran etexilate for the treatment and prophylaxis of patients with arterial and venous thromboembolic disorders, acute coronary syndromes and other medical conditions is warranted.     

Stroke thrombolysis in patients taking dabigatran

Stroke thrombolysis is becoming a common practice in Australian and New Zealand hospitals. There are no established guidelines for thrombolysis of patients who are taking dabigatran, and accurate medication reconciliation may not be possible. Patients with normal activated partial thromboplastin time are unlikely to have clinically significant dabigatran concentration in the blood. For safest outcomes, we suggest incorporating thrombin time assay for acute stroke patients suspected to be taking dabigatran.     

Treatment of visceral leishmaniasis: a review of current treatment practices

Introduction: In the Randomized Evaluation of Long-term Anticoagulant Therapy (RE-LY) trial, dabigatran 150 mg was shown to be superior to warfarin for the prevention of stroke or systemic embolism. However, there are some concerns with the RE-LY trial, such as its open-label design, potential unblinding of “blinded” adjudicators, the use of concomitant warfarin–aspirin (ASA), the disparity between baseline use of nonselective NSAIDs; the high unequal rate of drop-outs; unaccounted drop-ins; high rates of major bleeds in warfarin-treated patients, despite being a low risk population; and rates of major bleeds that do not match historic warfarin trials. Furthermore, although dabigatran offers potential advantages versus warfarin, there are disadvantages that must be taken into consideration before a patient is switched from the latter to the former. This review will summarize the flaws of the RE-LY trial as well as the clinically important advantages and disadvantages of dabigatran and warfarin.

Areas covered: This review examines the differences between dabigatran and warfarin in terms of side effects, drug–drug interactions, drug–food interactions, and potential reasons for using one anticoagulant rather than the other. The main focus of this review is a discussion of the design, procedures and results of the RE-LY trial.

Expert opinion: There seem to be major flaws with the RE-LY trial. A double-blinded trial should be performed testing dabigatran against warfarin to verify the results of the RE-LY trial.