Monitoring anticoagulant therapy with new oral agents

Conservative management of massive rivaroxaban overdose: A case report and literature review

In the cases of acute rivaroxaban overdose, conservative management without prothrombin complex concentrate or other coagulation factors may be sufficient if renal function is normal and there is no bleeding.

Direct-acting oral anti-coagulants in dental practice: A Retrospective Observational Study (Part 1)

OBJECTIVES

The objective of this retrospective observational study was to determine the incidence of direct-acting oral anti-coagulant (DOA) use in patients receiving invasive dental procedures. The secondary objective was to investigate the precautionary measures implemented and the post/intraoperative complications associated with DOA use.

METHODS

Electronic record database, Axium, was retrospectively reviewed, and patients using NGOA and treated between 2010 and 2017 were identified. Charts of patients who underwent invasive dental procedures were further reviewed to investigate the preoperative/intraoperative precautionary measures taken and identify any intraoperative/postoperative complications.

RESULTS

A total of 130 patients were identified, with their annual number steadily rising from 12 in 2011 to 52 in 2016. Among those, 64 patients (49.23%) underwent invasive dental procedures. Pretreatment medical consults were obtained in all patients undergoing invasive procedures; however, only 7 (10.94%) were instructed to discontinue their DOA. Preoperative laboratory testing was obtained for two patients. Intraoperatively, 34 (53.13%) cases of excessive bleeding were reported, all were locally controlled with hemostatic agents. Only 4 instances of postoperative complications were documented.

CONCLUSIONS

Despite the rise in the use of DOA, there is no consistent pattern for preoperative laboratory testing and DOA discontinuations. Expert consensus may be of great importance to develop practice guidelines.

Towards Personalized Antithrombotic Treatments: Focus on P2Y12 Inhibitors and Direct Oral Anticoagulants

Oral anticoagulants and antiplatelet drugs are commonly prescribed to lower the risk of cardiovascular diseases, such as venous and arterial thrombosis, which represent the leading causes of mortality worldwide. A significant percentage of patients taking antithrombotics will nevertheless experience bleeding or recurrent ischemic events, and this represents a major public health issue. Cardiovascular medicine is now questioning the one-size-fits-all policy, and more personalized approaches are increasingly being considered. However, the available tools are currently limited and they are only moderately able to predict clinical events or have a significant impact on clinical outcomes. Predicting concentrations of antithrombotics in blood could be an effective means of personalization as they have been associated with bleeding and recurrent ischemia. Target concentration interventions could take advantage of physiologically based pharmacokinetic (PBPK) and population-based pharmacokinetic (POPPK) models, which are increasingly used in clinical settings and have attracted the interest of governmental regulatory agencies, to propose dosages adapted to specific population characteristics. These models have the benefit of combining parameters from different sources, such as experimental in vitro data and patients' demographic, genetic, and physiological in vivo data, to characterize the dose-concentration relationships of compounds of interest. As such, they can be used to predict individual drug exposure. In the near future, these models could therefore be a valuable means of predicting personalized antithrombotic blood concentrations and, hopefully, of preventing clinical non-response or bleeding in a given patient. Existing approaches for personalization of antithrombotic prescriptions will be reviewed using practical examples for P2Y₁₂ inhibitors and direct oral anticoagulants. The review will additionally focus on the existing PBPK and POPPK models for these two categories of drugs. Lastly, we address potential scenarios for their implementation in clinics, along with the main limitations and challenges.

Directly Acting Oral Anticoagulants for the Prevention of Stroke in Atrial Fibrillation in England and Wales: Cost-Effectiveness Model and Value of Information Analysis

Objectives. Determine the optimal, licensed, first-line anticoagulant for prevention of ischemic stroke in patients with non-valvular atrial fibrillation (AF) in England and Wales from the UK National Health Service (NHS) perspective and estimate value to decision making of further research. Methods. We developed a cost-effectiveness model to compare warfarin (international normalized ratio target range 2-3) with directly acting (or non-vitamin K antagonist) oral anticoagulants (DOACs) apixaban 5 mg, dabigatran 150 mg, edoxaban 60 mg, and rivaroxaban 20 mg, over 30 years post treatment initiation. In addition to death, the 17-state Markov model included the events stroke, bleed, myocardial infarction, and intracranial hemorrhage. Input parameters were informed by systematic literature reviews and network meta-analysis. Expected value of perfect information (EVPI) and expected value of partial perfect information (EVPPI) were estimated to provide an upper bound on value of further research. Results. At willingness-to-pay threshold £20,000, all DOACs have positive expected incremental net benefit compared to warfarin, suggesting they are likely cost-effective. Apixaban has highest expected incremental net benefit (£7533), followed by dabigatran (£6365), rivaroxaban (£5279), and edoxaban (£5212). There was considerable uncertainty as to the optimal DOAC, with the probability apixaban has highest net benefit only 60%. Total estimated population EVPI was £17.94 million (17.85 million, 18.03 million), with relative effect between apixaban versus dabigatran making the largest contribution with EVPPI of £7.95 million (7.66 million, 8.24 million). Conclusions. At willingness-to-pay threshold £20,000, all DOACs have higher expected net benefit than warfarin but there is considerable uncertainty between the DOACs. Apixaban had the highest expected net benefit and greatest probability of having highest net benefit, but there is considerable uncertainty between DOACs. A head-to-head apixaban versus dabigatran trial may be of value.

Evaluation of activated charcoal and lipid emulsion treatment in model of acute rivaroxaban toxicity

AIM

Reducing or reversing the toxicity effects of new oral anticoagulants is an important question.The purpose of the present study is to evaluate the effect of lipid emulsion (LE) and Activated Charcoal (AC) therapy on the intoxication of rivaroxaban, on mice.

METHODS

Adult male Balb/c mice weighing approximately 30g were used in the study. Seven groups were assigned, with six mice in each group. Groups were defined; given only rivaroxaban, given only LE, given only AC, after the administration of rivaroxaban LE applied group in the 1st hour, after the administration of rivaroxaban LE applied group in the 3rd hour, after the administration of rivaroxaban AC applied group in the1st hour, after the administration of rivaroxaban AC applied group in the 1st hour and LE applied group in the 3rd hour. PT and Anti-Factor Xa activity were measured in all blood samples from subjects.

RESULTS

A statistically significant difference was found when all groups were compared in terms of mean PT values and Anti-FactorXa values. However, no statistically significant difference was found in the mean PT and Anti-FactorXa values when only rivaroxaban administrated group and after the administration of rivaroxaban LE and/or AC applied groups were compared one to one. No deaths occurred in groups during the observation.

CONCLUSION

Although the administration of either AC or LE alone or in combination resulted in a decrease in the mean values of PT and anti-Factor Xa, in case of rivaroxaban toxicity, but one-to-one comparison of the groups was not statistically significant.

Contemporary utilization of antithrombotic therapy for stroke prevention in patients with atrial fibrillation: an audit in an Australian hospital setting

BACKGROUND

To document antithrombotic utilization in patients with nonvalvular atrial fibrillation (NVAF), particularly, recently approved NOACs (nonvitamin K antagonist oral anticoagulants) and warfarin; and identify factors predicting the use of NOACs versus warfarin.

METHODS

A retrospective audit was conducted in an Australian hospital. Data pertaining to inpatients diagnosed with atrial fibrillation (AF) admitted between January and December 2014 were extracted. This included patient demographics, risk factors (stroke, bleeding), social history, medical conditions, medication history, medication safety issues, medication adherence, and antithrombotic prescribed at admission and discharge.

RESULTS

Among 199 patients reviewed, 84.0% were discharged on antithrombotics. Anticoagulants (± antiplatelets) were most frequently (52.0%) prescribed (two-thirds were prescribed warfarin, the remainder NOACs), followed by antiplatelets (33.0%). Among 41 patients receiving NOACs, 59.0% were prescribed rivaroxaban, 24.0% dabigatran, and 17.0% apixaban. Among patients aged 75 years and over, antiplatelets were most frequently used (37.0%), followed by warfarin (33.0%), then NOACs (14.0%). Compared with their younger counterparts, patients aged 75 years and over were significantly less likely to receive NOACs (14.0% versus 28.0%, p = 0.01). Among the 'most eligible' patients (Congestive Cardiac Failure, Hypertension (, Age ⩾ 75 years, Age= 65-74 years, Diabetes Mellitus, Stroke/ Transient Ischaemic Attack/ Thromboembolism, Vascular disease, Sex female[CHA2DS2-VASc] score ⩾2 and no bleeding risk factors), 46.0% were not anticoagulated on discharge. Patients with anaemia (68.0% versus 86.0%, p = 0.04) or a history of bleeding (65.0% versus 87.0%, p = 0.01) were less likely to receive antithrombotics compared with those without these risk factors. Warfarin therapy was less frequently prescribed among patients with cognitive impairment compared with patients with no cognitive issues (12.0% versus 23.0%, p = 0.01). Multivariate logistic regression modelling identified that patients with renal impairment were 3.6 times more likely to receive warfarin compared with NOACs (odds ratio = 3.6, 95% confidence interval = 0.08-0.90, p = 0.03, 60.0% correctly predicted; Cox and Snell R2 = 0.51, Nagelkerke R2 = 0.69).

CONCLUSION

Despite the availability of NOACs, warfarin remains a preferred treatment option, particularly among patients with renal impairment. The high proportion of eligible patients still being prescribed antiplatelet therapy or 'no therapy' needs to be addressed.

Model-Based Assessment Using Conventional Bioequivalence Limits to Ensure Safety and Efficacy of Rivaroxaban in Patients Undergoing Hip or Knee Replacement

We evaluated whether the current bioequivalence limit is adequate to ensure safety and efficacy of rivaroxaban in patients under total hip arthroplasty and total knee arthroplasty based on its model informed benefit/risk profile. Clinical data from a total of 7145 patients from 3 phase 2 and 4 phase 3 clinical trials were included in the current model-based exposure-response analysis. The relationships between rivaroxaban exposure measurements (ie, minimum or trough, maximum, average concentration, and area under the concentration-time curve [AUC] at steady state) and clinical outcomes (ie, the probabilities of major bleeding [MB] and venous thromboembolism [VTE]) were modeled using NONMEM 7.3. Model evaluation was performed using predictive checks and nonparametric bootstrap. Simulations were conducted to assess the study objectives. A shallow relationship was observed between explored exposure measurements within the tested dose range and the probability of VTE following rivaroxaban treatment. Trough concentrations were found to be a statistically significant predictor of the probability of MB. This relationship was better described using a power function. Model validation confirmed model adequacy. Based on the simulations results, the relative risk of MB of a hypothetical test product (with 20% change in AUC) will not statistically differ from the brand name drug. Twenty percent AUC variations do not change the relative risk of MB and is unlikely to compromise efficacy of therapy. A generic drug of rivaroxaban passing the typical bioequivalence assessment is expected to have similar safety and efficacy as the brand name drug.

In vitro and ex vivo Measurement of Prophylactic Dabigatran Concentrations with a New Ecarin-Based Thromboelastometry Test

BACKGROUND

An increasing number of oral anticoagulants has been approved, including dabigatran etexilate (DE). DE is a direct thrombin inhibitor that requires no routine monitoring, but, if necessary (e.g. urgent surgery etc.), the diluted thrombin time measured with Hemoclot® has shown reliable results. So far, no point-of-care (PoC) assay is available to measure DE effects. The EcaTEM assay uses ecarin to initiate the coagulation cascade at the step of thrombin generation and measures the clotting time (CT) by thromboelastometry.

METHODS

This study investigated the correlation of the EcaTEM with standard laboratory assays in dabigatran-treated patients. Ten patients undergoing total hip or knee arthroplasty were included in the study. DE for thromboprophylaxis was started 4 h after surgery. Blood samples were taken before surgery as well as 2, 6 and 12 h after ingestion on the 3rd postoperative day. Dabigatran concentration (Hemoclot), activated partial thromboplastin time, thrombin time and CT EcaTEM were measured.

RESULTS

Only CT EcaTEM and Hemoclot showed a correlation > 0.75 for all measurements.

CONCLUSION

CT EcaTEM appears a valid PoC method parameter to detect thrombin inhibition and thus the presence of dabigatran beside diluted thrombin time at different concentration levels. This may represent an opportunity to identify the presence of dabigatran, e.g., in emergency situations.