Does protamine chloride neutralize low molecular weight heparin sufficiently?

Enhanced Antiviral Function of Magnesium Chloride-Modified Heparin on a Broad Spectrum of Viruses

Previous studies reported on the broad-spectrum antiviral function of heparin. Here we investigated the antiviral function of magnesium-modified heparin and found that modified heparin displayed a significantly enhanced antiviral function against human adenovirus (HAdV) in immortalized and primary cells. Nuclear magnetic resonance analyses revealed a conformational change of heparin when complexed with magnesium. To broadly explore this discovery, we tested the antiviral function of modified heparin against herpes simplex virus type 1 (HSV-1) and found that the replication of HSV-1 was even further decreased compared to aciclovir. Moreover, we investigated the antiviral effect against the new severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) and measured a 55-fold decreased viral load in the supernatant of infected cells associated with a 38-fold decrease in virus growth. The advantage of our modified heparin is an increased antiviral effect compared to regular heparin.

A review of the role of anticoagulation in the treatment of peripheral arterial disease

Peripheral arterial disease (PAD) is a major medical/surgical problem associated with high risk for coronary heart disease (CHD). Anticoagulation plays a significant role in the management of the PAD patient. However, evidence-based medicine supports only select anticoagulants, mainly antiplatelet agents. The available anticoagulant classes, their individual medications, and the mechanisms of action are described. Dextran 40, platelet glycoprotein (GP) IIb/IIIa receptor antagonists, direct thrombin (factor IIa, FIIa) inhibitors, and factor Xa (FXa) inhibitors do not, at this juncture, appear to have a significant role to play in the PAD patient. Aspirin has been used in PAD patients for a few decades, as has warfarin, but the role of warfarin is very limited. An attempt has been made to place each medication and its function in context all the way to the present with oral direct thrombin (FIIa) and FXa inhibitors described. These inhibitors may ultimately play an, as yet, undefined role in PAD. Specific use of anticoagulants in PAD patients is described and aspirin still stands out as a fundamental therapy. The thienopyridines, especially clopidogrel, have their established place and there is some evidence for benefit from the use of clopidogrel in dual therapy with aspirin. Dipyridamole, especially with aspirin as dual therapy, and cilostazol also have their evidence-based niches. The main role played by warfarin is for the patient with a vein graft in the arterial circulation. Heparin retains significant procedural importance. For now, Class I, Level of Evidence A center around aspirin for the PAD patient with clopidogrel, an alternative agent.

Novel concatameric heparin-binding peptides reverse heparin and low-molecular-weight heparin anticoagulant activities in patient plasma in vitro and in rats in vivo

Patients given unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH) for prophylaxis or treatment of thrombosis sometimes suffer serious bleeding. We showed previously that peptides containing 3 or more tandem repeats of heparin-binding consensus sequences have high affinity for LMWH and neutralize LMWH (enoxaparin) in vivo in rats and in vitro in citrate. We have now modified the (ARKKAAKA)n tandem repeat peptides by cyclization or by inclusion of hydrophobic tails or cysteines to promote multimerization. These peptides exhibit high-affinity binding to LMWH (dissociation constant [Kd], ≈ 50 nM), similar potencies in neutralizing anti–Factor Xa activity of UFH and enoxaparin added to normal plasma in vitro, and efficacy equivalent to or greater than protamine. Peptide (ARKKAAKA)3VLVLVLVL was most effective in all plasmas from enoxaparin-treated patients, and was 4- to 20-fold more effective than protamine. Several other peptide structures were effective in some patients' plasmas. All high-affinity peptides reversed inhibition of thrombin-induced clot formation by UFH. These peptides (1 mg/300 g rat) neutralized 1 U/mL anti–Factor Xa activity of enoxaparin in rats within 1 to 2 minutes. Direct blood pressure and heart rate measurements showed little or no hemodynamic effect. These heparin-binding peptides, singly or in combination, are potential candidates for clinical reversal of UFH and LMWH in humans.

Use of low-molecular-weight heparins in the management of acute coronary artery syndromes and percutaneous coronary intervention

CONTEXT

Low-molecular-weight heparins (LMWHs) possess several potential pharmacological advantages over unfractionated heparin as an antithrombotic agent.

OBJECTIVE

To systematically summarize the clinical data on the efficacy and safety of LMWHs compared with unfractionated heparin across the spectrum of acute coronary syndromes (ACSs), and as an adjunct to percutaneous coronary intervention (PCI).

DATA SOURCES

We searched MEDLINE for articles from 1990 to 2002 using the index terms heparin, enoxaparin, dalteparin, nadroparin, tinzaparin, low molecular weight heparin, myocardial infarction, unstable angina, coronary angiography, coronary angioplasty, thrombolytic therapy, reperfusion, and drug therapy, combination. Additional data sources included bibliographies of articles identified on MEDLINE, inquiry of experts and pharmaceutical companies, and data presented at recent national and international cardiology conferences.

STUDY SELECTION

We selected for review randomized trials comparing LMWHs against either unfractionated heparin or placebo for treatment of ACS, as well as trials and registries examining clinical outcomes, pharmacokinetics, and/or phamacodynamics of LMWHs in the setting of PCI. Of 39 studies identified, 31 fulfilled criteria for analysis.

DATA EXTRACTION

Data quality was determined by publication in the peer-reviewed literature or presentation at an official cardiology society-sponsored meeting.

DATA SYNTHESIS

The LMWHs are recommended by the American Heart Association and the American College of Cardiology for treatment of unstable angina/non-ST-elevation myocardial infarction. Clinical trials have demonstrated similar safety with LMWHs compared with unfractionated heparin in the setting of PCI and in conjunction with glycoprotein IIb/IIIa inhibitors. Finally, LMWHs show promise as an antithrombotic agent for the treatment of ST-elevation myocardial infarction.

CONCLUSIONS

The LMWHs could potentially replace unfractionated heparin as the antithrombotic agent of choice across the spectrum of ACSs. In addition, they show promise as a safe and efficacious antithrombotic agent for PCI. However, further study is warranted to define the benefit of LMWHs in certain high-risk subgroups before their use can be universally recommended.

The use of specific antidotes as a response to bleeding complications during anticoagulant therapy for venous thromboembolism

When a bleeding complication occurs during therapy with heparin or vitamin K antagonists, there is an option to give a specific antidote. Several new anticoagulants have been developed that are likely to have some risk of bleeding complications, for which no specific antidotes are available. Interestingly, it is unknown how often the use of an antidote is necessary in clinical practice. We investigated 1877 patients treated for venous thromboembolism included in three large clinical trials, of which 181 (9.6%) had a total of 225 adjudicated bleeding episodes; 46 hemorrhages being designated as major. Some form of antidote was given to 26 (14.4%) patients with a hemorrhage. Of the patients with at least one major hemorrhage, 19 (41.3%) received an antidote. Vitamin K was given to 23 (1.2%) patients, one (0.05%) patient received protamin sulfate and seven (0.4%) patients received fresh frozen plasma. The use of antidotes was comparable for initial and long-term treatment. Antidotes were statistically significantly more frequently given in Canada as compared to other participating countries. Vitamin K was more frequently given in case of a higher international normalized ratio value. Although antidotes against anticoagulant treatment are widely available, our analysis shows that in only a very small number of patients a direct, or slow-acting antidote to reverse the anticoagulant effect was used.

Neutralization of the antithrombotic effects of heparin and Fraxiparin by protamine sulfate

In general, the in vitro anti Xa activity of low molecular weight heparins is neutralized to a lesser degree than the anti Xa activity of unfractionated heparin. To determine whether these differences occur in vivo, a rabbit stasis thrombosis model and a rat laser-induced thrombosis model were utilized. In the laser model, a similar degree of neutralization of the antithrombotic activity of heparin and Fraxiparin was obtained. However, in the stasis thrombosis model, significant antithrombotic activity of Fraxiparin remained after equigravimetric protamine administration. Ex vivo APTT, thrombin time, Heptest, amidolytic anti Xa and anti IIa assays were performed. A coefficient (r = .806) was obtained for the correlation of Heptest activity to antithrombotic effect in the stasis thrombosis model, while the coefficients obtained for the other tests ranged from .152-.570. However, after neutralization by protamine, the thrombin time exhibited the highest correlation coefficient (r = .685) between ex vivo activity and residual antithrombotic effect. Since Fraxiparin retains antithrombotic activity after protamine administration, clinical benefit may be observed for this low molecular weight heparin as compared to unfractionated heparin after neutralization.

Study on neutralization of low molecular weight heparin (LHG) by protamine sulfate and its neutralization characteristics

The neutralizing effects of protamine sulfate (PS) on anticoagulant activities of low molecular weight heparin (LHG) and conventional sodium heparin (Heparin) were investigated. The in vitro anti-factor Xa and APTT-prolonging activities of Heparin were almost completely neutralized by PS, whereas the activities of LHG remained partially intact in the presence of PS. Crossed immunoelectrophoresis of antithrombin III (AT III) and affinity chromatography of LHG- and Heparin-cellulose showed that AT III was substantially less dissociated from its binding to LHG than to Heparin in the presence of PS. As in vitro, the in vivo anticoagulant activities of Heparin administered i.v. to rabbits were almost completely neutralized by PS, while the anti-factor Xa and APTT-prolonging activities of LHG remained partially intact in the presence of PS. The thrombin time-prolonging activity of LHG, however, was completely inhibited by PS. Since the bleeding effect of Heparin or LHG is considered mainly due to its anti-thrombin activity, PS may be used as an agent to neutralize LHG, as in the case of Heparin, when bleeding happens to occur during LHG treatment.