A fluorescent probe assay (Heparin Red) for direct detection of heparins in human plasma.

Heparins are widely used anticoagulant drugs. The current monitoring practice for heparin in plasma, such as the chromogenic anti-factor Xa assay, relies on heparin-triggered activation of antithrombin, an inhibitor of coagulation proteases. Such assays are not applicable to the detection of non-anticoagulant heparins, an emerging class of drug candidates for therapeutic applications unrelated to anticlotting activity. This study describes the application of a commercially available fluorescent probe assay (Heparin Red) for the direct and sensitive detection of the "chemical" heparin in plasma, independent of any anticoagulant activity. The quantification range is about 0-5 µg/mL for both unfractionated heparin (corresponding to 0-1 IU/mL) and the low molecular weight heparin enoxaparin. The Heparin Red assay is of particular value for the quantification of non-anticoagulant heparins, as exemplified by the low molecular weight heparin derivative tafoxiparin and a N-desulfated-N-reacetylated heparin. Heparin octa- and decasaccharides are also detected. Graphical abstract Heparin quantification in plasma by mixing the sample with the Heparin Red reagent and fluorescence readout.

Biosimilars of low-molecular-weight heparin products: fostering competition or reducing 'biodiversity'?

The term 'biosimilars' is used to qualify products developed to be similar to an original biological drug. Biosimilars are much more complicated to develop than a generic version of small-molecule drugs and this is especially true for low-molecular-weight heparins (LMWHs). Evidence on the antithrombotic management of acute coronary syndromes (ACS) showed that the introduction into the market of biosimilars approved on the basis of simple biological criteria, without robust data from comparative clinical trials, may be hazardous. Moreover, the mixtures of LMWH polysaccharide chains, some immunoallergic properties and potential contamination during the extraction process raise safety concerns. As was the case for the biosimilar erythropoietin, there is the risk that only copies of the most commercially successful LMWHs will be marketed, thus jeopardizing the 'biodiversity' now ensured by the presence of several LMWHs, each with unique features that support the use of an individual LMWH as first-choice therapy in certain categories of patients.

Anticoagulation in patients with impaired renal function and with haemodialysis. Anticoagulant effects, efficacy, safety, therapeutic options.

Patients with impaired renal function are exposed to an increased risk for bleeding complications depending on the amount of the anticoagulant eliminated by the kidneys. The elimination of unfractionated heparins, vitamin K antagonists and argatroban is only minimally influenced by a reduced renal function. Low-molecular weight heparins, fondaparinux, danaparoid, hirudins and non-vitamin K antagonist oral anticoagulants (NOAC) cause a variably increased bleeding risk in renal impairment. Dose reductions are recommended for all of these anticoagulants in renal impairment, some are even contraindicated at certain levels of renal impairment. Their benefit over the conventional anticoagulants is preserved if renal dosing is employed. For end-stage renal disease patients specific treatment regimens are required.

Anticoagulation in patients with impaired renal function and with haemodialysis.

Patients with impaired renal function are exposed to an increased risk for bleeding complications depending on the amount of the anticoagulant eliminated by the kidneys. The elimination of unfractionated heparins, vitamin K antagonists and argatroban is only minimally influenced by a reduced renal function. Low-molecular weight heparins, fondaparinux, danaparoid, hirudins and nonvitamin K antagonist oral anticoagulants (NOAC) cause a variably increased bleeding risk in renal impairment. Dose reductions are recommended for all of these anticoagulants in renal impairment, some are even contraindicated at certain levels of renal impairment. Their benefit over the conventional anticoagulants is preserved if renal dosing is employed. For end-stage renal disease patients specific treatment regimens are required.

Clinical trials with new oral anticoagulants. Additive value of indirect comparisons also named network meta-analyses.

To compare the efficacy and safety of the new oral anticoagulants (NOAC), ideally head-to-head clinical trials should be performed. Given the expense of such an undertaking, it is highly unlikely that such a comparison would be performed. Therefore, there is a need for an unbiased comparative assessment of the benefits and risks of the NOACs, based on the available trial data. Indirect or mixed treatment comparisons may be an useful tool to overcome these limitations also known as network meta-analysis (NMA). The aim of this paper is to give an overview on published NMAs for dabigatran, rivaroxaban and apixaban, each assessed against warfarin in patients with atrial fibrillation, and against enoxaparin in patients undergoing total knee and total hip replacement surgery, in order to obtain insights into the comparability of the adopted methodological techniques.

Comparison of efficacy and safety of dabigatran, rivaroxaban and apixaban in patients with atrial fibrillation using network meta-analysis.

AIM: A network meta-analysis of the three new oral anticoagulants was performed from the three trials comparing dabigatran, rivaroxaban and apixaban with warfarin in patients with atrial fibrillation. METHODS: Data were extracted of the RE-LY study of dabigatran 110 mg bid and dabigatran 150 mg bid, the ROCKET AF trial of rivaroxaban and the ARISTOTLE trial of apixaban for the composite outcome of ischemic stroke and systemic embolism, for major bleeding, intracerebral bleeding, mortality and myocardial infarction. RESULTS: Dabigatran (150 mg bid) showed superior efficacy in preventing ischemic stroke plus systemic embolism to dabigatran (110 mg bid, P=0.0364) and rivaroxaban (P=0.0388). Apixaban had equivalent efficacy with rivaroxaban and dabigatran (either dose). Apixaban was safer (less major bleeding) than dabigatran (150 mg bid, P=0.036) or rivaroxaban (P=0.0002). Intracerebral hemorrhage occurred with equal frequency for all agents except for rivaroxaban (higher risk than dabigatran 110 mg bid, P=0.0070). Myocardial infarction occurred less frequently with rivaroxaban and apixaban compared to either dose of dabigatran (all P<0.05). CONCLUSION: All-cause mortality was not different for any agent or regimen. In the absence of head-to-head comparisons, this network meta-analysis suggests that apixaban and dabigatran 110 mg bid may offer the best benefit-risk balance for stroke prevention in non-valvular atrial fibrillation. Dabigatran 150 mg bid may be preferred for patients with a high risk for embolism.

[Anticoagulation in the elderly]. / Antikoagulation im Alter.

The recommendations for anticoagulation in over 80 years old patients are based on the thromboembolic/bleeding risk relation. They add to the published recommendations for the specific indications. Low-molecular-weight heparin (LMWH) is used to prevent thromboembolism postoperatively. Compression stockings and/or intermittent pneumatic compression are used if bleeding risk is very high. The dose is increased starting at day two if the thromboembolic risk is very high. Bleeding and thromboembolic risks are re-evaluted daily. The antithrombotic therapy is adjusted accordingly. Prophylaxis of thromboembolism in patients with acute illnesses and bedrest is performed according postoperative care. Two-thirds of therapeutic doses of low-molecular-weight heparin are used to treat acute venous thromboembolism. Reduced renal function (creatinine clearance <30 ml/ min for most LMWHs or <20 ml/min for tinzaparin) should result in a further reduction of dose. Intensity and duration of prophylaxis of recurrent events with vitamin K antagonist or LMWH in malignancy follow current or herein described recommendations. Patients with atrial fibrillation are treated with vitamin K antagonists adjusted to an INR of 2-3 for prophylaxis of embolism. Further details of anticoagulant therapy should be in agreement with the national or international recommendations.

Recommendations on biosimilar low-molecular-weight heparins.

Based on the results of large clinical trials, several low-molecular-weight heparins (LMWHs) have been approved for prophylaxis and the treatment of venous and arterial thromboembolism. As a result of expiration or pending expiration of patent protection of the originator LMWHs, many generic or biosimilar LMWHs have been approved in some countries and more are likely to be approved elsewhere. Their greater availability may reduce the treatment costs. The Working Party on Requirements for Development of Biosimilar LMWHs of the Subcommittee on Control of Anticoagulation, Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis has reached a consensus on recommendations to ensure the quality of biosimilar LMWHs as compared with the originator LMWHs.

Ximelagatran for treatment and prophylaxis of recurrent events in deep vein thrombosis.

The treatment of acute venous thromboembolism and prophylaxis of recurrent events with heparin/low molecular weight heparin followed by vitamin K antagonists is limited by several factors. Oral direct thrombin inhibitors (ODTIs) showed a better pharmacological activity and might be an alternative in the treatment of venous thromboembolism. The Thrombin Inhibition in Venous Thromboembolism (THRIVE) program performed some studies developing the ODTI ximelagatran for this indication, and it is presented in the overview. The aim of the THRIVE I study was the dose finding, and that of the THRIVE IV study the applicability in hemodynamic stabile pulmonary embolism. A prospective, randomized, double blind trial was performed to compare oral ximelagatran with enoxaparin/warfarin for a 6-month treatment of acute venous thrombosis (THRIVE II and V). A second double blind study compared ximelagatran with placebo over 18 months after a 6-month anticoagulant therapy of acute deep vein thrombosis. The efficacy and safety of treatment of patients with acute deep venous thrombosis who received 2 infinity 36 mg ximelagatran was not inferior to that of patients who received a conventional anticoagulant for prophylaxis of recurrent events over 6 months. Ximelagatran 2 infinity 24 mg significantly reduced recurrent thromboembolic events compared to placebo without increasing the risk for hemorrhage. A reversible symptomless increase of alanine aminotransferase occurs in 6% to 9.6% of patients between months 2 and 4. The results of the follow-up studies suggest that thromboembolic events may recur in patients with acute venous thromboembolism after termination of treatment with both vitamin K antagonists and ximelagatran.

Impact of ABO blood groups on tirofiban mediated inhibition of platelet function.

Previous investigations revealed that ABO blood groups are associated with divergent concentrations of several coagulation factors. Concentrations of von Willebrand factor (vWF) and factor VIII are lower in individuals with blood group O as compared to subjects with blood group A, B or AB which might result in a reduced inhibition of platelet aggregation. The aim of the present in-vitro-investigation was to elucidate the impact of ABO blood group dependent vWF concentrations on tirofiban mediated inhibition of GPIIb/IIIa function. Platelet function was measured with the platelet function analyzer PFA-100 at baseline and at increasing concentrations of tirofiban and stratified for blood group O vs. A. If measured with the collagen/epinephrine cartridge, blood group O was associated with a prolonged mean baseline closure time in comparison with blood group A (175.8 +/- 64.9 s vs. 121.4 +/- 33.4 s, p = 0.037) which was paralleled by reduced concentrations of vWF and factor VIII. In contrast, no differences in closure time (227.6 +/- 76.1 s vs. 223.9 +/- 81.9 s, p = 0.96) could be found in the presence of tirofiban (0.1 microg/ml). Thus, tirofiban mediated GP IIb/IIIa receptor antagonism as determined with the PFA-100 seems to be independent on plasma concentration of vWF.