Battle of oral anticoagulants in the field of atrial fibrillation scrutinized from a clinical practice (the real world) perspective

Effects of sulfotanshinone sodium injection on the pharmacokinetics and pharmacodynamics of warfarin in rats in vivo

This study was to explore the effects of sulfotanshinone sodium injection (SSI) on the pharmacokinetics and pharmacodynamics of warfarin in rats.The studies of single dose and multiple dose of warfarin were designed to assess the interaction between warfarin and SSI. Rats were divided into different groups randomly and administered with warfarin in the absence or presence of SSI. Prothrombin time (PT) and activated partial thromboplastin time (APTT) values were detected by blood coagulation analyzer, and international normalized ratio (INR) values were calculated. Plasma concentrations of warfarin enantiomers were determined by UPLC-MS/MS method, pharmacokinetic parameters were calculated.The single-dose study demonstrated that the repeated doses of SSI alone had no effect on PT, APTT and INR values, but had a significant effect on PT and INR values produced by a single dose of warfarin, APTT values were unaffected. The C_max, AUC of R-warfarin and S-warfarin were reduced, t_1/2 were shortened. The multiple-dose study showed that PT, APTT, INR values, and the C_max and AUC of R-warfarin and S-warfarin decreased significantly after administration of SSI.The finding implied that SSI could accelerate warfarin metabolism and weaken its anticoagulation. However, human SSI-warfarin interaction studies need to be conducted to confirm this finding.

Carbon-13 and carbon-14 labeled dabigatran etexilate and tritium labeled dabigatran

Dabigatran etexilate or pradaxa, a novel oral anticoagulant, is a reversible, competitive, direct thrombin inhibitor. It is used to prevent strokes in patients with atrial fibrillation and the formation of blood clots in the veins (deep venous thrombosis) in adults who have had an operation to replace a hip or a knee. Pradaxa is the only novel oral anticoagulant available with both proven superiority to warfarin and a specific reversal agent for use in rare emergency situations. The detailed description of the synthesis of carbon-13 and carbon-14 labeled dabigatran etexilate, and tritium labeled dabigatran is described. The synthesis of carbon-13 dabigatran etexilate was accomplished in eight steps and in 6% overall yield starting from aniline-¹³ C₆ . Ethyl bromoacetate-1-¹⁴ C was the reagent of choice in the synthesis of carbon-14 labeled dabigatran etexilate in six steps and 17% overall yield. Tritium labeled dabigatran was prepared using either direct tritium incorporation under Crabtree's catalytic conditions or tritium-dehalogenation of a diiodo-precursor of dabigatran.

Recovery of visual function after administration of dabigatran etexilate

A 46-year-old Caucasian female underwent pars plana vitrectomy (ppv) for retinal detachment. After the procedure, the patient could only distinguish hand movements; the condition was tentatively diagnosed as nonarteritic anterior ischemic optic neuropathy. Conventional treatment with systemic corticosteroids and acetylsalicylic acid was ineffective and yielded substantial steroid-related side effects. Additional administration of 2 × 110 mg dabigatran etexilate (Pradaxa(®)), a novel direct thrombin inhibitor, resulted in a prompt and marked improvement of visual acuity, which indicated improved blood flow in the central vessels of the optic nerve. Dabigatran etexilate may provide a promising alternative for the treatment of postprocedural vision loss after ppv.

[Dabigatran: transforming the management of oral anticoagulation]

The utility of oral anticoagulation with warfarin in thromboembolic disease has been demonstrated for several decades, although these drugs have significant problems in terms of adequate control, interactions and risk of bleeding. In the last decade, new anticoagulants have emerged. The first was dabigatran with a demonstrated anticoagulant effect approaching the ideal anticoagulant profile. The view that dabigatran transforms oral anticoagulation therapy has arisen from the RE-VOLUTION program, with more than 34000 patients analyzed. This program has confirmed the value of oral anticoagulation with dabigatran compared with other anticoagulants; this drug eliminates all the drawbacks of warfarin, benefitting both patients and the healthcare system. The growth of the aging population has increased the number of risk situations in which anticoagulation is used. There is now a drug that meets the criteria for the ideal anticoagulant, transforming the management of oral anticoagulation. The findings demonstrated with dabigatran in prior studies are progressively being transferred to clinical practice. Following the usual development of new drugs, and according to the latest Laurence Desmond stages, results in agreement with those of previous studies are expected, namely, indisputable improvements in oral anticoagulation for patients and the health system.

The new oral anti-coagulants and the phase 3 clinical trials - a systematic review of the literature

Background

Anticoagulation with vitamin K antagonists such as warfarin has historically been used for the long term management of patients with thromboembolic disease. However, these agents have a slow onset of action which requires bridging therapy with heparin and its analogues, which are available only in parenteral route. To overcome these limitations, new oral anticoagulants such as factor Xa inhibitors and direct thrombin inhibitors have been developed. The aim of this article is to systematically review the phase 3 clinical trials of new oral anticoagulants in common medical conditions.

Methods

We searched PubMed (Medline) from January 2007 to February 2013 using “Oral anticoagulants”, “New oral anticoagulants”, “Randomized controlled trial”, “Novel anticoagulants”, “Apixaban”, “Rivaroxaban”, “Edoxaban”, “Dabigatran etexilate”, “Dabigatran” and a combination of the above terms. The available evidence from the phase 3 RCTs was summarized on the basis of individual drug and the medical conditions categorized into “atrial fibrillation”, “acute coronary syndrome”, “orthopedic surgery”, “venous thromboembolism” and “medically ill patients”.

Results

Apixaban, rivaroxaban and dabigatran have been found to be either non-inferior or superior to enoxaparin in prophylaxis of venous thromboembolism in knee and hip replacement with similar bleeding risk, superior to warfarin for stroke prevention in atrial fibrillation with significant reduction in the risk of major bleeding, non-inferior to aspirin for reducing cardiovascular death and stroke in acute coronary syndrome with significant increase in the risk of major bleed. Rivaroxaban and dabigatran are also superior to the conventional agents in the management of symptomatic venous thromboembolism. However, compared to enoxaparin, apixaban and rivaroxaban use lead to significantly increased bleeding risk in medically ill patients. Additional studies evaluating the specific reversal agents of these new drugs for the management of life-threatening bleeding or other adverse effects are necessary.

Conclusion

Considering their pharmacological properties, their efficacy and bleeding complications, the new oral agents offer a net favourable clinical profile in orthopedic surgery, atrial fibrillation, acute coronary syndrome and increase the risk of bleeding in critically ill patients. Further studies are necessary to determine the long term safety and to identify the specific reversal agents of these new drugs.

In vitro assessment, using thrombin generation, of the applicability of prothrombin complex concentrate as an antidote for Rivaroxaban

BACKGROUND

Rivaroxaban has been approved as an antithrombotic agent for prevention of venous thromboembolism with specific indications. At present no antidote is appointed and no guidelines have been formulated for the measurement of Rivaroxaban reversal.

OBJECTIVES

In the present study, we have evaluated the influence of prothrombin complex concentrate (PCC) on the anticoagulant effects of Rivaroxaban as measured by prothrombin time (PT) and thrombin generation tests (TGTs).

METHODS

Plasma and whole blood samples from healthy volunteers were spiked with Rivaroxaban (up to 800 μg L(-1) ) and PCC was added to these samples in concentration ranges as used clinically to reverse the effects of vitamin K antagonists. PT, endogenous thrombin potential (ETP) and calibrated automated thrombography (CAT) assays were performed with varying tissue factor (TF) concentrations.

RESULTS

Addition of PCC to Rivaroxaban-spiked samples did not result in normalization of PT and TGT lag time/T-Lag in ETP and CAT, respectively. In contrast, normalization of ETP and CAT area under the curve did occur. However, the response to PCC addition was strongly TF concentration dependent and in whole blood less PCC was required for Rivaroxaban reversal as compared with plasma.

CONCLUSIONS

Prothrombin complex concentrate does not neutralize the lengthening effect on PT and TGT lag time/T-Lag of Rivaroxaban anticoagulated blood in vitro; however, total thrombin potential could be normalized. Response of the different TGTs in this respect is assay condition dependent. Therefore, prospective studies are needed to clarify which assay condition and parameter describes in vivo hemostasis best in patients on Rivaroxaban who are treated with PCC.

Comparing new anticoagulants

For years, the pharmaceutical industry has been trying to find a safe and effective drug to replace warfarin. Although warfarin is an effective anticoagulant, its pharmacology, adverse effects, and risk profiles dictate that patients taking this medication must be monitored judiciously. The US Food and Drug Administration has approved two drugs for commercial use, dabigatran and rivaroxaban, that will compete directly with warfarin for use in specific indications. Because of direct marketing to patients, physicians are being asked to comment on these new medications. This brief review illustrates the data available for the two new drugs when compared to warfarin for the specified indications. For some patients, these drugs may be highly beneficial and offer an excellent alternative to warfarin. For others, warfarin may still be the preferred drug.

A guidance pathway for the selection of novel anticoagulants in the treatment of atrial fibrillation

Oral anticoagulation with vitamin K antagonists has served as the primary treatment for the prevention of stroke and systemic embolization in patients with atrial fibrillation (AF) for decades. Over the past several years, multiple novel oral anticoagulants targeting key mediators of coagulation, including thrombin and factor Xa, have been developed. Specifically, agents targeting thrombin (dabigatran) and factor Xa (apixaban and rivaroxaban) have either reached late stages of clinical development (apixaban) or have received approval (dabigatran, rivaroxaban) by the US Food and Drug Administration for use in patients with nonvalvular AF. The promising results derived from large-scale clinical trials with these agents compared to warfarin expand the available therapeutic options for the prevention of stroke and systemic embolization in this rapidly increasing patient population. Here we present a general guidance pathway for the initiation and selection of oral anticoagulants in patients with AF.

Dabigatran etexilate: a pharmacoeconomic review of its use in the prevention of stroke and systemic embolism in patients with atrial fibrillation

This article provides an overview of the clinical profile of oral dabigatran etexilate (Pradaxa®, Pradax™) [hereafter referred to as dabigatran] when used for the prevention of stroke and systemic embolism in patients with nonvalvular atrial fibrillation (AF), followed by a review of cost-utility analyses of dabigatran in this patient population. Dabigatran (110 or 150 mg twice daily) demonstrated noninferiority versus adjusted-dose warfarin with regard to the prevention of stroke and systemic embolism (primary endpoint) in patients with AF in the RE-LY trial, and the 150 mg twice-daily dosage was significantly more effective than warfarin for this endpoint, as well as most other efficacy endpoints. The incidence of major bleeding was generally similar in patients receiving dabigatran 150 mg twice daily or warfarin, but was lower in patients receiving dabigatran 110 mg twice daily. With regard to other bleeding endpoints, dabigatran was generally associated with lower rates than warfarin, except for gastrointestinal major bleeding. Dabigatran (both dosages) was associated with a higher incidence of dyspepsia than warfarin. Results of modelled cost-utility analyses from several countries from the perspective of a healthcare payer over a lifetime (or 20-year) time horizon and primarily based on data from the RE-LY trial were generally consistent. All but one analysis demonstrated that twice-daily dabigatran 150 mg (or age-adjusted, sequential dosing) was cost effective with regard to the incremental cost per QALY gained relative to adjusted-dose warfarin in the prevention of stroke and systemic embolism in AF patients, as the results were below generally accepted cost-effectiveness thresholds. In contrast, the incremental cost per QALY gained for dabigatran 110 mg twice daily versus warfarin exceeded cost-effectiveness thresholds in all studies except one. Sensitivity analyses suggested that the cost utility of dabigatran versus warfarin was generally robust to variations in the majority of parameters. However, the incremental cost per QALY gained for dabigatran versus warfarin improved when levels of international normalized ratio control in warfarin recipients decreased and when the baseline level of risk of stroke increased.