Clinical pharmacokinetics and pharmacodynamics of the oral direct thrombin inhibitor dabigatran etexilate

Design and rationale for the DIVERSITY study: An open-label, randomized study of dabigatran etexilate for pediatric venous thromboembolism

BACKGROUND

The current standard of care (SOC) for pediatric venous thromboembolism (VTE) comprises unfractionated heparin (UFH), or low-molecular-weight heparin (LMWH) followed by LMWH or vitamin K antagonists, all of which have limitations. Dabigatran etexilate (DE) has demonstrated efficacy and safety for adult VTE and has the potential to overcome some of the limitations of the current SOC. Pediatric trials are needed to establish dosing in children and to confirm that results obtained in adults are applicable in the pediatric setting.

OBJECTIVES

To describe the design and rationale of a planned phase IIb/III trial that will evaluate a proposed dosing algorithm for DE and assess the safety and efficacy of DE versus SOC for pediatric VTE treatment.

PATIENTS/METHODS

An open-label, randomized, parallel-group noninferiority study will be conducted in approximately 180 patients aged 0 to <18 years with VTE, who have received initial UFH or LMWH treatment and who are expected to require ≥3 months of anticoagulation therapy. Patients will receive DE or SOC for 3 months. DE will be administered twice daily as capsules, pellets, or an oral liquid formulation according to patient age. Initial doses will be calculated using a proposed dosing algorithm.

RESULTS

There will be two coprimary endpoints: a composite efficacy endpoint comprising the proportion of patients with complete thrombus resolution, freedom from recurrent VTE and VTE-related mortality, and a safety endpoint: freedom from major bleeding events.

CONCLUSION

Findings will provide valuable information regarding the efficacy and safety of DE for the treatment of pediatric VTE. ClinicalTrials.gov registration number: NCT01895777.

The Renal Elimination Pathways of the Dabigatran Reversal Agent Idarucizumab and its Impact on Dabigatran Elimination

Idarucizumab, a humanized monoclonal antibody fragment (Fab), provides rapid and sustained reversal of dabigatran-mediated anticoagulation. Idarucizumab and dabigatran are mainly eliminated via the kidneys. This analysis aimed to characterize the renal elimination of idarucizumab and investigate the influence of idarucizumab on the pharmacokinetics (PK) of dabigatran and vice versa. Studies were conducted in 5/6 nephrectomized rats, in human volunteers with and without renal impairment, and in a porcine liver trauma model. In both rats and humans, renal impairment increased idarucizumab exposure and initial half-life but did not affect its terminal half-life. Urinary excretion of unchanged idarucizumab increased with increasing idarucizumab dose, suggesting saturation of renal tubular reuptake processes at higher doses. The PK of idarucizumab was unaffected by dabigatran. In contrast, idarucizumab administration resulted in redistribution of dabigatran to the plasma, where it was bound and inactivated by idarucizumab. Urinary excretion of dabigatran after administration of idarucizumab was delayed, but total dabigatran excreted in urine was unaffected. Idarucizumab and dabigatran were eliminated together via renal pathways.

Dabigatran in nonvalvular atrial fibrillation: from clinical trials to real-life experience

: Atrial fibrillation is the most common arrhythmia in over-midlife patients. In addition to systolic heart failure, cerebral thromboembolism represents the most dramatic complication of this rhythm disorder, contributing to morbidity and mortality. Traditionally, anticoagulation has been considered the main strategy in preventing stroke and systemic embolism in atrial fibrillation patients and vitamin K-dependent antagonists have been widely used in clinical practice. Recently, the development of direct oral anticoagulants has certainly improved the management of this disease, providing, for the first time, the opportunity to go beyond vitamin K-dependent antagonists limits. In the RE-LY trial, dabigatran 150 mg twice daily was superior to warfarin in the prevention of stroke or systemic embolism and dabigatran 110 mg twice daily was noninferior. Both doses greatly reduced hemorrhagic stroke, and dabigatran 110 mg twice daily significantly reduced major bleeding compared with warfarin. Based on these results, dabigatran, a direct thrombin inhibitor, was the first direct oral anticoagulant to receive the regulatory approval for nonvalvular atrial fibrillation patients. To date, a specific reversal agent has just been approved as an antidote for this molecule. This review provides a summary of randomized trials, postmarket registries and specific clinical-settings summary on dabigatran in nonvalvular atrial fibrillation.

Real-Life Peak and Trough Dabigatran Plasma Measurements over Time in Hospitalized Geriatric Patients with Atrial Fibrillation

BACKGROUND

Few geriatric patients were included in studies on direct oral anticoagulants and data on dabigatran concentration and safety are needed in this population. Our objectives were to evaluate peak and trough dabigatran plasma concentrations over time in a geriatric population and to identify factors associated with dabigatran plasma concentrations and to assess the relationship with bleeding events.

METHODS

Peak and trough dabigatran plasma concentration were performed 4,8,15,30,45 days after inception of dabigatran treatment in 68 consecutive patients ≥75 years old hospitalized in a geriatric hospital with atrial fibrillation. Bleeding events were monitored for 1 year.

RESULTS

Mean age was 85.8(5.1) years old and 76.5% were women. Overall, 541 dabigatran plasma measurements (270 peak, 271 trough) were performed. Mean dabigatran concentrations of the 5 sequential measurements ranged 106-146ng/mL for peak and 66-84ng/mL for trough. Renal failure was associated with high peak and trough dabigatran concentration. Inter- and intra-individual coefficients of variation were 59.5% and 44.7% for peak and 74.5% and 44.6% for trough. Participants in the lower two tertiles of dabigatran concentration at day 8 (D8) remained below the 90th percentile (243.9ng/ml) on the next measurements. Bleeding events were associated with high trough dabigatran concentrations. Trough dabigatran concentration at D8>243.9ng/mL significantly predicted bleeding.

CONCLUSION

In this geriatric population, renal function and low albumin were associated with dabigatran concentrations. Despite large variability, participants in the lower two tertiles of dabigatran concentration at D8 remained below the 90th percentile on the following measurements. D8 dabigatran trough concentration≥243.9ng/mL identified patients at risk of bleeding.

Vitamin K antagonists

For the last decades, anticoagulation for stroke prevention in atrial fibrillation (AF) as well as for the prophylaxis and long-term treatment of venous thromboembolism has been entirely based on vitamin K antagonists (VKA). Although very effective under optimal conditions, long-term treatment with these drugs is flawed by the fact that the time in the therapeutic range frequently is suboptimal due to biological factors, drug interactions and compliance.

The direct thrombin inhibitor dabigatran, as well as the direct FXa inhibitors rivaroxaban and apixaban provide more consistent anticoagulation and have proven their efficacy and safety against VKAs in several large scale randomized clinical trials for stroke prevention in atrial fibrillation as well as for the treatment and prevention of venous thromboembolism. In view of these convincing data and other advantages such as the lack of mandatory monitoring and only few drug interactions,VKAs will most likely be replaced in a majority of patients for these indications. Based on the most recent trial evidence, the current review discusses the role of VKA treatmentand that of the novel anticoagulants.

Comparison of the ecarin chromogenic assay and diluted thrombin time for quantification of dabigatran concentrations

Essentials Routine monitoring is unnecessary but measuring dabigatran levels is helpful in certain situations. We compared ecarin chromogenic assay (STA-ECA-II) and dilute thrombin time (dTT) in patient samples. Both tests provided accurate measurements over a wide range of dabigatran concentrations. Adoption of STA-ECA-II and dTT into routine clinical practice will improve patient care.

SUMMARY

Background Although routine coagulation monitoring is unnecessary, measuring plasma dabigatran concentrations can be useful for detecting drug accumulation in renal failure or overdose, assessing the contribution of dabigatran to serious bleeding, planning the timing of urgent surgery or intervention, or determining the suitability for thrombolytic therapy for acute ischemic stroke. Dabigatran concentrations can be quantified using chromogenic or clot-based tests, such as the ecarin chromogenic assay (ECA) and the diluted thrombin time (dTT), respectively. Objective The purpose of this study was to compare the results of these assays with dabigatran concentrations measured by the reference standard of mass spectrometry in samples from 50 dabigatran-treated patients collected at peak and trough after at least 4 months of drug intake. Methods Drug levels measured with either the STA Ecarin Chromogenic Assay-II (STA-ECA-II) or dTT were linearly correlated with those determined by mass spectrometry over a wide range of concentrations. Results and Conclusions For detection of levels below 50 ng mL-1 both tests have specificities of at least 96%, suggesting that they accurately detect even low levels of drug. Therefore, regardless of whether a chromogenic or clot-based platform is preferred, the STA-ECA-II and dTT are useful tests for measuring dabigatran concentrations. Unfortunately, neither test is licensed by the United States Food and Drug Administration. Although approved in other jurisdictions, the dTT and STA-ECA-II are not widely or rapidly available in most hospitals. Therefore, cooperation between regulators and hospitals is urgently needed to render these tests readily available to inform patient care.

Reversal of rivaroxaban anticoagulation by haemostatic agents in rats and primates

Rivaroxaban is an oral, direct factor Xa inhibitor for the management of thromboembolic disorders. Despite its short half-life, the ability to reverse rivaroxaban anticoagulation could be beneficial in life-threatening emergencies. The potential of prothrombin complex concentrate (PCC; Beriplex®), activated PCC (aPCC; FEIBA®) or recombinant activated factor VII (rFVIIa; NovoSeven®) to reverse rivaroxaban in rats and baboons was investigated. Anaesthetised rats pre-treated with intravenous rivaroxaban (2 mg/kg) received intravenous rFVIIa (100/400 μg/kg), PCC (25/50 U/kg) or aPCC (50/100 U/kg) after initiation of bleeding. Clotting times and bleeding times (BTs) were recorded. Rivaroxaban was administered as an intravenous 0.6 mg/kg bolus followed by continuous 0.6 mg/kg/hour infusion in baboons. Animals received intravenous aPCC 50 U/kg (2 U/kg/minute) or rFVIIa 210 μg/kg. BT and clotting parameters were measured. In rats pre-treated with high-dose rivaroxaban, PCC 50 U/kg, aPCC 100 U/kg and rFVIIa 400 μg/kg significantly reduced BT vs rivaroxaban alone (5.4 ± 1.4-fold to 1.5 ± 0.4-fold [p<0.05]; 3.0 ± 0.4-fold to 1.4 ± 0.1-fold [p<0.001]; and 3.5 ± 0.7-fold to 1.7 ± 0.2-fold [p<0.01] vs baseline, respectively). In baboons pre-infused with rivaroxaban and then given aPCC, BT increased by 2.0 ± 0.2-fold and aPCC returned BT to baseline for the duration of its infusion. rFVIIa reduced BT from 2.5 ± 0.3-fold over baseline to 1.7 ± 0.3-fold over baseline. Prolongation of prothrombin time was reduced by PCC, aPCC and rFVIIa in both species. Rivaroxaban reduced thrombin-antithrombin levels; application of PCC and aPCC, but not rFVIIa, increased these levels. In conclusion, PCC, aPCC or rFVIIa have the potential to reverse the anticoagulant and anti-haemostatic effects of rivaroxaban.

Safety, tolerability and clinical pharmacology of dabigatran etexilate in adolescents

Venous thromboembolism (VTE) incidence is increasing among children owing to many factors, including improved diagnosis of VTE. There is a need for alternative treatment options. Our objective was to investigate the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of dabigatran etexilate in adolescents with VTE. Adolescents aged 12 to <18 years (n = 9) who successfully completed planned treatment for primary VTE were administered dabigatran etexilate twice daily for three days; initially 1.71 (± 10%) mg/kg (80% of a 150 mg/70 kg twice daily adult dose), followed by 2.14 (± 10%) mg/kg (target adult dose adjusted for patient’s weight), if there were no safety concerns. No bleeding events, deaths or drug-related serious adverse events (AEs) were reported; three treatment-emergent AEs, all gastrointestinal-related, occurred in two patients. In these adolescent patients with normal renal function, presumed steady-state trough plasma concentrations of dabigatran were low (geometric mean dosenormalised total dabigatran plasma concentration: 0.493 ng/ml/mg at 72 hours). Total dabigatran concentrations were well predicted by the RE-LY® population PK model (94% of trough concentrations were within the 80% prediction interval). The relationship between total dabigatran plasma concentration, diluted thrombin time and ecarin clotting time (ECT) was linear; the relationship with activated partial thromboplastin time (aPTT) was non-linear. Adult population PK/PD models predicted the adolescent concentration–ECT and –aPTT relationships well. In conclusion, dabigatran etexilate was generally well tolerated, except for occurrence of dyspepsia in two patients, over the three-day treatment period. The dabigatran PK/PD relationship observed in adolescent patients was similar to that in adult patients.

Institution where work was performed: Main clinical study site: Children’s Hospital of Eastern Ontario, Ottawa, Ontario, Canada.

This study is registered at ClinicalTrials.gov (NCT00844415).

A combined pharmacometric analysis of dabigatran etexilate in healthy volunteers and patients with atrial fibrillation or undergoing orthopaedic surgery

Dabigatran etexilate is the orally bioavailable pro-drug of dabigatran, a direct thrombin inhibitor. Using data from eight clinical studies in healthy volunteers and patients with non-valvular atrial fibrillation (AF) or undergoing orthopaedic surgery (OS), population pharmacokinetic (PK) and pharmacodynamic (PD) models were developed to investigate whether the PK and PD of dabigatran differ across different populations. In both healthy volunteers (n=80) and patients (n=1,965), the PK of dabigatran was best described by a two-compartment disposition model with first-order absorption and elimination. Renal function was the only covariate shown to have a clinically relevant impact on dabig-atran exposure. The patient PK model was successfully applied in predicting exposure observed in the RE-LY trial evaluating dabigatran treatment in patients with non-valvular AF. The relationship between dabigatran plasma concentrations and activated partial thromboplastin time in healthy volunteers and patients (n=762) was best described with a combination of a linear model and a maximum effect (Emax) model, consistent with previous reports. PK/PD relationships were robust across the various populations tested and were not affected by any of the covariates examined. In summary, the PK of dabigatran is sufficiently consistent to allow extrapolation of data generated in healthy volunteers to patients with AF or undergoing OS.

A randomised study in healthy volunteers to investigate the safety, tolerability and pharmacokinetics of idarucizumab, a specific antidote to dabigatran

Idarucizumab, a monoclonal antibody fragment that binds dabigatran with high affinity, is in development as a specific antidote for dabigatran. In this first-in-human, single-rising-dose study, we investigated the pharmacokinetics, safety and tolerability of idarucizumab. Healthy male volunteers aged 18–45 years received between 20 mg and 8 g idarucizumab as a 1-hour intravenous infusion in 10 sequential dose groups, or 1, 2 or 4 g idarucizumab as a 5-minute infusion. Subjects within each dose group were randomised 3:1 to idarucizumab or placebo. A total of 110 randomised subjects received study drug (27 placebo, 83 idarucizumab). Peak and total exposure to idarucizumab increased proportionally with dose. Maximum plasma concentrations were achieved near the end of infusion, followed by a rapid decline, with an initial idarucizumab half-life of ∼45 minutes. For the 5-minute infusions, this resulted in a reduction of plasma concentrations to less than 5 % of peak within 4 hours. Idarucizumab (in the absence of dabigatran) had no effect on coagulation parameters or endogenous thrombin potential. Overall adverse event (AE) frequency was similar for idarucizumab and placebo, and no relationship with idarucizumab dose was observed. Drug-related AEs (primary endpoint) were rare (occurring in 2 placebo and 3 idarucizumab subjects) and were mostly of mild intensity; none of them resulted in study discontinuation. In conclusion, the pharmacokinetic profile of idarucizumab meets the requirement for rapid peak exposure and rapid elimination, with no effect on pharmacodynamic parameters. Idarucizumab was safe and well tolerated in healthy males.

Clinical trial registration: http://clinicaltrials.gov/ct2/show/NCT01688830?term=NCT01688830&rank=1 (NCT01688830).

Sex-Specific Comparative Effectiveness of Oral Anticoagulants in Elderly Patients With Newly Diagnosed Atrial Fibrillation

BACKGROUND

Sex-specific comparative effectiveness of direct oral anticoagulants among patients with nonvalvular atrial fibrillation is not known. Via this retrospective cohort study, we assessed the sex-specific, comparative effectiveness of direct oral anticoagulants (rivaroxaban and dabigatran), compared to each other and to warfarin among patients with atrial fibrillation.

METHODS AND RESULTS

Elderly (aged ≥66 years) Medicare beneficiaries enrolled in Medicare Part D benefit plan from November 2011 to October 2013 with newly diagnosed atrial fibrillation formed the study cohort (65 734 [44.8%] men and 81 137 [55.2%] women). Primary outcomes of inpatient admissions for ischemic strokes and major bleeding were compared across the 3 drugs (rivaroxaban: 20 mg QD, dabigatran: 150 mg BID, or warfarin) using 3-way propensity-matched samples. In men, rivaroxaban use decreased stroke risk when compared with warfarin use (hazard ratio, 0.69; 95% confidence interval, 0.48-0.99; P=0.048) and dabigatran use (hazard ratio, 0.66; 95% confidence interval, 0.45-0.96; P=0.029) and was associated with a similar risk of any major bleeding when compared with warfarin and dabigatran. In women, although ischemic stroke risk was similar in the 3 anticoagulant groups, rivaroxaban use significantly increased the risk for any major bleeding when compared with warfarin (hazard ratio, 1.20; 95% confidence interval, 1.03-1.42; P=0.021) and dabigatran (hazard ratio, 1.27; 95% confidence interval, 1.09-1.48; P=0.011).

CONCLUSIONS

The reduced risk of ischemic stroke in patients taking rivaroxaban, compared with dabigatran and warfarin, seems to be limited to men, whereas the higher risk of bleeding seems to be limited to women.

Safety, pharmacokinetics and pharmacodynamics of idarucizumab, a specific dabigatran reversal agent in healthy Japanese volunteers: a randomized study

BACKGROUND

Idarucizumab is a humanized monoclonal antibody fragment that specifically binds with high affinity to dabigatran.

OBJECTIVES

This study investigated the safety, tolerability and pharmacokinetics of idarucizumab alone and with dabigatran at steady state, and the effects of idarucizumab on dabigatran-induced anticoagulation.

PATIENTS/METHODS

This was a two-part, phase I, randomized, placebo-controlled, double-blind, rising-dose trial in healthy Japanese males. Part 1: 32 subjects (males) received single idarucizumab doses (1, 2, 4 or 8 g [n=6/dose group]) or placebo (n=2/dose group). Part 2: 48 males received dabigatran (220 mg bid) followed by idarucizumab (n=9/dose group) 1, 2, 4 or 5 g (2×2.5 g), or placebo (n=3/dose group). Anti-idarucizumab antibodies (ADAs) and idarucizumab effect on anticoagulation parameters (diluted thrombin time [dTT], ecarin clotting time [ECT], activated partial thromboplastin time [aPTT] and thrombin time [TT]) were assessed.

RESULTS

No adverse events were reported in subjects receiving idarucizumab. After single doses of idarucizumab (alone or at steady state of dabigatran), maximum plasma concentration was achieved around the end of each infusion. Mean all anticoagulation parameters fell below the upper limit of normal immediately after idarucizumab infusion in all dose groups; the effect was sustained at 4 and 2×2.5 g over the entire measurement period until 72 h. At 1- and 2-g doses, partial return of the anticoagulant effect occurred. Idarucizumab alone had no effect on coagulation parameters. Treatment-emergent ADAs occurred in 6/60 males receiving idarucizumab.

CONCLUSIONS

Idarucizumab infusion achieved immediate, complete and sustained reversal of dabigatran-induced anticoagulation in Japanese volunteers. Idarucizumab was well tolerated with no procoagulant effects. Trial registration number: ClinicalTrials.gov NCT02028780 (completed).

Dabigatran-Induced Massive Spontaneous Hemothorax

Spontaneous hemothorax due to anticoagulant use is extremely rare in clinical practice. Dabigatran is a novel anticoagulant to prevent stroke or thromboembolic episodes in patients with nonvalvular atrial fibrillation. We report on an 83-year-old man who received dabigatran therapy (110 mg twice daily) for 7 months and developed massive spontaneous hemothorax and acute renal failure. The patient was admitted to the hospital with complaint of a dull ache in the chest and dyspnea. Chest computed tomography scan revealed massive pleural effusion in the left hemithorax with atelectasis. Acute renal failure was observed 4 days later after admission. Almost 2500 mL of blood was repeatedly drained by ultrasound-guided thoracocentesis, followed by a dramatic decrease in serum red blood cell count, hemoglobin and hematocrit. After excluding other possible causes, diagnostic withdrawal was performed for dabigatran, and plasma transfusion was conducted to supply the lost blood volume. A causal relationship was established, because the patient's renal function gradually improved and no further pleural effusion developed after dabigatran was discontinued. This is a rare case report of massive spontaneous hemothorax caused by dabigatran. Therefore, practitioners should be aware of hemothorax as a potential complication of dabigatran therapy.

Dabigatran reversal with idarucizumab in a patient undergoing heart transplantation: first European report

Background

Dabigatran is a direct thrombin inhibitor with a favorable effectiveness and safety profile when compared to vitamin K antagonists, both in randomized trials and real world registries of atrial fibrillation patients. Yet, physicians’ fear of high bleeding risk scenarios in daily clinical practice still precludes a more widespread use of oral anticoagulation. We hereby report a successful case of dabigatran reversal with the novel monoclonal antibody fragment idarucizumab in a patient undergoing heart transplantation.

Case presentation

A 45-year old male patient on dabigatran for atrial fibrillation thromboprophylaxis was enlisted for heart transplantation due to end-stage ischemic heart failure. Upon donor availability and suitability and following the last intake of the drug 12 h previously, activated partial thromboplastin time was measured and found to be elevated. After general anesthesia and before extracorporeal circulation, idarucizumab was administered as two boluses of 2.5 g. Orthotopic heart transplantation ensued under full heparinization and cardiopulmonary bypass. Total chest tube output was 1125 mL after 3 days and 4 units of fresh frozen plasma and one platelet pool were administered in the operating room without further need for blood products. The post-operative period was uneventful.

Conclusions

Idarucizumab was associated with an effective hemostasis in the setting of heart transplantation. Dabigatran may be considered as an alternative to vitamin K antagonists in heart transplant candidates with an indication for oral anticoagulation.

A dabigatran etexilate phospholipid complex nanoemulsion system for further oral bioavailability by reducing drug-leakage in the gastrointestinal tract

Dabigatran etexilate (DE) is insoluble at neutral pH values but soluble at low pH values due to protonation, which is the major cause for the poor bioavailability of commercial DE products. Here, we first developed a DE nanoemulsion system and improved dissolution in simulated intestinal fluids by encapsulating DE into an oil phase, but 35.8% of the drug still leaked out. Further, we prepared a DE-phospholipid complex (DE-PC) to enhance lipophilicity and solubility of DE. The resulting DE-PC nanoemulsions significantly (P<0.05) reduced drug leakage and subsequent precipitation. As a result, the relative bioavailability of DE-PC nanoemulsions increased to 147.3% and 606.6% compared to DE nanoemulsions and commercial DE products, respectively. Thus, the presently developed drug-phospholipid complex nanoemulsion system is a promising drug delivery system for improving the oral bioavailability of pH-dependent soluble drugs.

Effect of New Oral Anticoagulants on Prescribing Practices for Atrial Fibrillation in Older Adults

OBJECTIVES

To determine the effect of new oral anticoagulants (NOACs) on prescribing practices in older adults with atrial fibrillation (AF).

DESIGN

Retrospective observational cohort study.

SETTING

Academic medical center in St. Louis, Missouri.

PARTICIPANTS

Individuals aged 75 and older with AF admitted to the hospital from October 2010 through September 2015 (N = 6,568, 50% female, 15% non-white).

MEASUREMENTS

Information on NOACs and warfarin prescribed at discharge was obtained from hospital discharge summaries, and linear regression was used to examine quarterly trends in their use. Multivariable logistic regression was used to assess independent predictors of anticoagulant use.

RESULTS

NOAC use increased over time (correlation coefficient (r) = 0.87, P < .001), warfarin use did not change (r = -0.16, P = .50), and overall anticoagulant use (NOACs and warfarin) increased (r = 0.68, P = .001). NOAC use increased over time in all age groups (75-79, 80-84, 85-89) except aged 90 and older, but increasing age attenuated the rate of NOAC uptake. There was no consistent relationship between age and warfarin or overall anticoagulant use, except that individuals aged 90 and older had consistently lower use. Overall, fewer than 45% of participants were prescribed an anticoagulant. In multivariable analysis, younger age, white race, female sex, higher hemoglobin, higher creatinine clearance, being on a medical service, hypertension, stroke or transient ischemic attack, no history of intracranial hemorrhage, and a modified HAS-BLED score of less than 3 increased the likelihood of receiving NOACs.

CONCLUSION

Prescription of anticoagulants for AF increased in older adults primarily because of an increase in the use of NOACs. Nonetheless, fewer than 45% of participants were prescribed an anticoagulant. Additional research is needed to optimize prescribing practices for older adults with AF.

Idarucizumab for Dabigatran Reversal - Full Cohort Analysis

BACKGROUND

Idarucizumab, a monoclonal antibody fragment, was developed to reverse the anticoagulant effect of dabigatran.

METHODS

We performed a multicenter, prospective, open-label study to determine whether 5 g of intravenous idarucizumab would be able to reverse the anticoagulant effect of dabigatran in patients who had uncontrolled bleeding (group A) or were about to undergo an urgent procedure (group B). The primary end point was the maximum percentage reversal of the anticoagulant effect of dabigatran within 4 hours after the administration of idarucizumab, on the basis of the diluted thrombin time or ecarin clotting time. Secondary end points included the restoration of hemostasis and safety measures.

RESULTS

A total of 503 patients were enrolled: 301 in group A, and 202 in group B. The median maximum percentage reversal of dabigatran was 100% (95% confidence interval, 100 to 100), on the basis of either the diluted thrombin time or the ecarin clotting time. In group A, 137 patients (45.5%) presented with gastrointestinal bleeding and 98 (32.6%) presented with intracranial hemorrhage; among the patients who could be assessed, the median time to the cessation of bleeding was 2.5 hours. In group B, the median time to the initiation of the intended procedure was 1.6 hours; periprocedural hemostasis was assessed as normal in 93.4% of the patients, mildly abnormal in 5.1%, and moderately abnormal in 1.5%. At 90 days, thrombotic events had occurred in 6.3% of the patients in group A and in 7.4% in group B, and the mortality rate was 18.8% and 18.9%, respectively. There were no serious adverse safety signals.

CONCLUSIONS

In emergency situations, idarucizumab rapidly, durably, and safely reversed the anticoagulant effect of dabigatran. (Funded by Boehringer Ingelheim; RE-VERSE AD ClinicalTrials.gov number, NCT02104947 .).

Anticoagulant Reversal and Anesthetic Considerations

Bleeding complications are a common concern with the use of anticoagulant agents. In many situations, reversing of neutralizing their effects may be warranted. Prothrombin complex concentrate replaces coagulation factors lowered by warfarin, as does fresh frozen plasma, but in a more concentrated form. Protamine negates the effect of heparin and combines chemically with heparin molecules to form an inactive salt. It also partially reverses the effects of low-molecular-weight heparin. Recombinant activated factor VII is a nonspecific procoagulant that activates the extrinsic clotting pathway, resulting in thrombin generation, but does not directly neutralize the activity of any of the new oral anticoagulants.

The Reversal of Direct Oral Anticoagulants in Animal Models

Several direct oral anticoagulants (DOACs), including direct thrombin and factor Xa inhibitors, have been approved as alternatives to vitamin K antagonist anticoagulants. As with any anticoagulant, DOAC use carries a risk of bleeding. In patients with major bleeding or needing urgent surgery, reversal of DOAC anticoagulation may be required, presenting a clinical challenge. The optimal strategy for DOAC reversal is being refined, and may include use of hemostatic agents such as prothrombin complex concentrates (PCCs; a source of concentrated clotting factors), or DOAC-specific antidotes (which bind their target DOAC to abrogate its activity). Though promising, most specific antidotes are still in development.Preclinical animal research is the key to establishing the efficacy and safety of potential reversal agents. Here, we summarize published preclinical animal studies on reversal of DOAC anticoagulation. These studies (n = 26) were identified via a PubMed search, and used rodent, rabbit, pig, and non-human primate models. The larger of these animals have the advantages of similar blood volume/hemodynamics to humans, and can be used to model polytrauma. We find that in addition to varied species being used, there is variability in the models and assays used between studies; we suggest that blood loss (bleeding volume) is the most clinically relevant measure of DOAC anticoagulation-related bleeding and its reversal.The studies covered indicate that both PCCs and specific reversal agents have the potential to be used as part of a clinical strategy for DOAC reversal. For the future, we advocate the development and use of standardized, clinically, and pharmacologically relevant animal models to study novel DOAC reversal strategies.

Oral Anticoagulant Use After Bariatric Surgery: A Literature Review and Clinical Guidance

Bariatric surgery may alter the absorption, distribution, metabolism, or elimination (disposition) of orally administered drugs via changes to the gastrointestinal tract anatomy, body weight, and adipose tissue composition. As some patients who have undergone bariatric surgery will need therapeutic anticoagulation for various indications, appropriate knowledge is needed regarding anticoagulant drug disposition and resulting efficacy and safety in this population. We review general considerations about oral drug disposition in patients after bariatric surgery, as well as existing literature on oral anticoagulation after bariatric surgery. Overall, available evidence on therapeutic anticoagulation is very limited, and individual drug studies are necessary to learn how to safely and effectively use the direct oral anticoagulants. Given the sparsity of currently available data, it appears most prudent to use warfarin with international normalized ratio monitoring, and not direct oral anticoagulants, when full-dose anticoagulation is needed after bariatric surgery.

Long-term treatment of cancer-associated thrombosis: the choice of the optimal anticoagulant

Patients with cancer-associated thrombosis (CAT) carry a higher risk of recurrence, bleeding and mortality as compared with non-cancer patients. The specific profiles of cancer patients, combining frequent co-morbidities, the use of anti-tumoral therapies and the cancer progression itself, represent a major therapeutic challenge for choosing a long-term anticoagulant treatment. This review discusses the practical basis of making a choice between the available drugs for a long-term antithrombotic strategy, linked to their pharmacology, mechanism of action, evidence of clinical benefits, and advantages and limitations in such a complex clinical context. In patients with cancer, low-molecular-weight heparins (LMWHs) are the preferred option for the secondary prevention of venous thromboembolism according to current guidelines, because their efficacy is significantly superior to vitamin K antagonists (VKAs). Even though LMWHs are effective and safe in cancer patients, they require daily subcutaneous injections, which may be problematic for a long-term therapy that may exceed 6 months' duration. Compared with VKAs, non-vitamin-K antagonist oral anticoagulants or direct oral anticoagulants (DOACs) are more target specific and do not require laboratory monitoring, whereas the oral route of administration makes them potentially attractive alternatives to LMWH. In randomized controlled trials in the general population DOACs have been shown to be non-inferior to VKAs in terms of efficacy with a lower rate of clinically relevant or major bleeding. However, given the limited number of cancer patients enrolled in these studies (with poorly defined active cancer), available trials are inconclusive regarding the usefulness of DOACs in the cancer setting. Ongoing head-to-head comparisons vs. LMWH in patients with CAT may allow an informed choice to be made regarding the DOAC option.

Evolving Treatments for Arterial and Venous Thrombosis: Role of the Direct Oral Anticoagulants

The direct oral anticoagulants (DOACs) represent a major advance in oral anticoagulant therapy and have replaced the vitamin K antagonists as the preferred treatment for many indications. By simplifying long-term anticoagulant therapy and improving its safety, the DOACs have the potential to reduce the global burden of thrombosis. Postmarketing studies suggest that the favorable results achieved with DOACs in the randomized controlled trials can be readily translated into practice, but highlight the need for appropriate patient, drug and dose selection, and careful follow-up. Leveraging on their success to date, ongoing studies are assessing the utility of DOACs for the prevention of thrombosis in patients with embolic stroke of unknown source, heart failure, coronary artery disease, peripheral artery disease, antiphospholipid syndrome, and cancer. The purpose of this article is to (1) review the pharmacology of the DOACs, (2) describe the advantages of the DOACs over vitamin K antagonists, (3) summarize the experience with the DOACs in established indications, (4) highlight current challenges and limitations, (5) highlight potential new indications; and (6) identify future directions for anticoagulant therapy.

Why Prodrugs and Propesticides Succeed

What are the advantages of bioactivation in optimizing drugs and pesticides? Why are there so many prodrugs and propesticides? These questions are examined here by considering compounds selected on the basis of economic value or market success in 2015. The 100 major drugs and 90 major pesticides are divided into ones acting directly and those definitely or possibly requiring bioactivation. Established or candidate prodrugs accounted for 19% of the total drug sales, with corresponding values of 20, 37, and 17% for proinsecticides, proherbicides, and profungicides. The 19 prodrugs acting in humans generally had better pharmacodynamic/pharmacokinetic properties for target enzyme, receptor, tissue, or organ specificity due to their physical properties (lipophilicity and stabilization). Bioactivation usually involved hydrolases or cytochrome P450 oxidation or reduction. Prodrugs considered are neuroactive aripiprazole, eletriptan, desvenlafaxin, lisdexamfetamine, quetiapine, and fesoterodine; cholesterol-lowering atorvastatin, ezetimibe, and fenofibrate; various prodrugs activated by esterases or sulfatases, ciclesonide, oseltamivir, dabigatran; omega-3 fatty acid ethyl esters and esterone sulfate; and five others with various targets (sofosbuvir, fingolimod, clopidogrel, dapsone, and sildenafil). The proinsecticides are the neuroactive chlorpyrifos, thiamethoxam, and indoxacarb, two spiro enol ester inhibitors of acetyl CoA carboxylase (ACCase), and the bacterial protein delta-endotoxin. The proherbicides considered are five ACCase inhibitors including pinoxaden and clethodim, three protox inhibitors (saflufenacil, flumioxazin, and canfentrazone-ethyl), and three with various targets (fluroxypyr, isoxaflutole, and clomazone). The profungicides are prothioconazole, mancozeb, thiophanate-methyl, dazomet, and fosetyl-aluminum. The prodrug and propesticide concept is broadly applicable and has created some of the most selective pharmaceutical and pest control agents, illustrated here by major compounds that partially overcome pharmacokinetic limitations of potency and selectivity in the corresponding direct-acting compounds. The challenges of molecular design extend beyond the target site fit to the bioactivatable precursor and the fascinating chemistry and biology matched against the complexity of life processes.

Novel oral anticoagulants in the management of coronary artery disease

Despite advances in interventional and pharmacologic therapy, survivors of myocardial infarction remain at an increased risk of subsequent cardiovascular events. Initial pharmacological management includes both platelet inhibition and parenteral anticoagulation, whereas long-term pharmacological therapy relies on antiplatelet therapy for prevention of thrombotic complications. Biomarkers showing ongoing thrombin generation after acute coronary syndromes suggest that anticoagulants may provide additional benefit in reducing cardiovascular events. We review the pharmacokinetics of novel anticoagulants, clinical trial results, the role of monitoring, and future directions for the use of novel oral anticoagulants in the treatment of coronary artery disease. Clinical trials have shown that long-term use of oral anticoagulants decreases the risk of cardiovascular events, but they do so at a cost of an increased risk of bleeding. Future studies will need to identify optimal treatment combinations for selected patients and conditions that address both the appropriate combination of therapy and the appropriate dosage of each agent when used in combination.

Drug-induced liver injury: Towards early prediction and risk stratification

Drug-induced liver injury (DILI) is a hot topic for clinicians, academia, drug companies and regulators, as shown by the steadily increasing number of publications and agents listed as causing liver damage (http://livertox.nih.gov/). As it was the case in the past decade with drug-induced QT prolongation/arrhythmia, there is an urgent unmet clinical need to develop tools for risk assessment and stratification in clinical practice and, in parallel, to improve prediction of pre-clinical models to support regulatory steps and facilitate early detection of liver-specific adverse drug events. Although drug discontinuation and therapy reconciliation still remain the mainstay in patient management to minimize occurrence of DILI, especially acute liver failure events, different multidisciplinary attempts have been proposed in 2016 to predict and assess drug-related risk in individual patients; these promising, albeit preliminary, results strongly support the need to pursue this innovative pathway.

An injectable in situ lipid phase transition system for sustained delivery of dabigatran etexilate with low burst release

The first report of dabigatran exilate sustained release injection that exhibited great potential in controlling initial burst release.

Direct oral anticoagulant considerations in solid organ transplantation: A review

For more than 60 years, warfarin was the only oral anticoagulation agent available for use in the United States. In many recent clinical trials, several direct oral anticoagulants (DOACs) demonstrated similar efficacy with an equal or superior safety profile, with some other notable benefits. The DOACs have lower inter- and intrapatient variability, much shorter half-lives, and less known drug-drug and drug-food interactions as compared to warfarin. Despite these demonstrated benefits, the use of DOACs has not gained uniform acceptance because of lack of supportive data in special patient populations, including recipients of solid organ transplants maintained on immunosuppression. This review describes the properties of several novel DOACs including their pharmacology and mechanisms of action as they relate to use among solid organ transplant recipients. We have particularly focused on (i) dosing in patients with impaired renal and hepatic function; (ii) considerations for drug-drug interactions with immunosuppressive medications; and (iii) management of the anticoagulated patients at the time of unplanned surgery. The risks and benefits of the use of DOACs in solid organ transplant recipients should be carefully evaluated prior to the introduction of these agents in this highly distinct patient population.

Use of novel oral anticoagulant agents in venous thromboembolism

New oral anticoagulants (NOAC) serve as alternatives for patients currently using warfarin for the prevention and treatment of venous thromboembolic (VTE) disease. This article provides a brief summary of the clinical use of these drugs as well as a review of the landmark clinical trials which evaluated described their safety and efficacy. As more data becomes available, a fundamental understanding of these medications will be vital to cardiovascular practitioners managing patients with VTE.

Association between statin use and ischemic stroke or major hemorrhage in patients taking dabigatran for atrial fibrillation

BACKGROUND

Dabigatran etexilate is a prodrug whose absorption is opposed by intestinal P-glycoprotein and which is converted by carboxylesterase to its active form, dabigatran. Unlike other statins, simvastatin and lovastatin are potent inhibitors of P-glycoprotein and carboxylesterase, and might either increase the risk of hemorrhage with dabigatran etexilate or decrease its effectiveness.

METHODS

We conducted 2 population-based, nested case-control studies involving Ontario residents 66 years of age and older who started dabigatran etexilate between May 1, 2012, and Mar. 31, 2014. In the first study, cases were patients with ischemic stroke; in the second, cases were patients with major hemorrhage. Each case was matched with up to 4 controls by age and sex. All cases and controls received a single statin in the 60 days preceding the index date. We determined the association between each outcome and the use of simvastatin or lovastatin, relative to other statins.

RESULTS

Among 45 991 patients taking dabigatran etexilate, we identified 397 cases with ischemic stroke and 1117 cases with major hemorrhage. After multivariable adjustment, use of simvastatin or lovastatin was not associated with an increased risk of stroke (adjusted odds ratio [OR] 1.33, 95% confidence interval [CI] 0.88 to 2.01). In contrast, use of simvastatin and lovastatin were associated with a higher risk of major hemorrhage (adjusted OR 1.46, 95% CI 1.17 to 1.82).

INTERPRETATION

In patients receiving dabigatran etexilate, simvastatin and lovastatin were associated with a higher risk of major hemorrhage relative to other statins. Preferential use of the other statins should be considered in these patients.

Prognostic Value of Red Blood Cell Distribution Width on Bleeding Events in Nonvalvular Atrial Fibrillation Patients Taking Dabigatran (110 mg b.i.d.) after Catheter Ablation

OBJECTIVES

Recent research has indicated that red blood cell distribution width (RDW) is associated with the prognosis of cardiovascular diseases such as chronic heart failure and coronary heart disease. We aimed to study the predictive value of RDW for bleeding events in patients with nonvalvular atrial fibrillation (NVAF) during the administration of 110 mg of dabigatran twice a day after catheter ablation.

METHODS

One hundred and seventy-two NVAF patients who were hospitalized and received catheter ablation in Jiangsu Provincial People's Hospital from January 2014 to January 2015 were enrolled (110 mg of dabigatran was administered orally to outpatients preoperatively twice a day for 3 weeks). The enrolled patients were divided into the high RDW (>12.8%) group (n = 85) and the low RDW (≤12.8%) group (n = 87) according to the median RDW. The activated partial thromboplastin time (APTT) at dabigatran trough concentration was also detected. Patients were followed up for 3 months to observe the occurrence of bleeding events, and the predictive value of RDW as well as APTT for bleeding events was assessed from receiver-operating characteristic (ROC) analyses.

RESULTS

In all patients, preoperatively, no bleeding events were observed and the APTT did not exceed twice the normal upper limit. Thirteen cases of bleeding events, all minor bleeding, occurred after a 3-month follow-up: 3 of gingival bleeding, 3 of urinary tract bleeding, 3 conjunctival hemorrhages and 4 subcutaneous hemorrhages. The incidence of bleeding events in the low RDW group was lower than in the high RDW group (3.4 vs. 11.8%, p = 0.039). The areas under the ROC curve for RDW and APTT to predict the occurrence of bleeding events were 0.737 (cutoff point 13.25%; p < 0.05) and 0.558 (p > 0.05), respectively.

CONCLUSION

RDW was associated with the occurrence of bleeding events in NVAF patients on dabigatran (110 mg twice a day) after ablation, while also being an independent predictor of bleeding events. RDW had superior predictive value for bleeding events over APTT when APTT did not exceed twice the normal upper limit.

Laboratory Monitoring: A Turning Point in the Use of New Oral Anticoagulants

Large clinical trials have demonstrated that new oral anticoagulants (NOACs) are at least as efficient as vitamin K antagonists (VKAs) in preventing thromboembolic events, while providing a better safety profile. The relatively stable pharmacokinetics and pharmacodynamics, the reduced reports on food and drug interactions, and the wide therapeutic windows of NOACs appear to provide a more predictable anticoagulant effect than that observed with VKAs, enabling the use of fixed doses without the need for monitoring. However, the safe implementation of NOACs may require additional judgment, and one should not have the erroneous impression that NOACs are free from interactions or that inter- and intra-individual variability is absent with NOACs. In fact, a consensus seems to have been reached concerning the usefulness of "circumstantial" testing in certain clinical scenarios. Recent data also suggest that factors such as intercurrent diseases, drug interactions, and inexplicable variability may occasionally alter the anticoagulant effect of NOACs. Furthermore, the issue of nonadherence, already high in VKA-treated patients, may represent an even greater clinical concern with NOACs, given their short half-lives. This review aims to underline the main arguments that support the need for NOAC monitoring, at least in selected categories of patients. Additionally, an overview of classic coagulation assays and novel laboratory techniques that may provide a tool for NOAC monitoring is also provided.

New Oral Anticoagulants in Nonvalvular Atrial Fibrillation

The choice of an oral anticoagulant (OAC) for patients with nonvalvular atrial fibrillation (NVAF) is a major and complex clinical decision taking into account the individual risk-benefit ratio and bearing in mind the chronicity of therapy. This review focuses on the safety and efficacy of new oral anticoagulants (NOACs) compared with conventional vitamin K antagonists (VKA) in patients with NVAF. Current data suggest that NOACs are at least as effective and safe as VKAs for most NVAF subjects. The NOACs do not mandate dietary restrictions and regular pharmacodynamic monitoring, and they seem to have lesser incidence of intracranial or fatal bleeding when compared with VKAs. However, both dabigatran 150 twice daily and rivaroxaban have a slightly higher incidence of gastrointestinal bleeding when compared with VKAs. The article will delineate the current knowledge as well as scientific gaps related to the choice and dosage of anticoagulation regimens for various NVAF subsets and will address certain common clinical scenarios requiring special considerations. The article also addresses the shortcomings of NOACs: lack of therapeutic pharmacokinetic and pharmacodynamic targets, absence of tools to assess compliance and efficacy, rigid and limited dosage options, and absence of effective and inexpensive reversal agents.