Activity Of Heparin Research Articles

Assessment of Heparin Anticoagulation Measured Using i-STAT and Hemochron Activated Clotting Time

Adequate anticoagulation, measured using activated clotting time (ACT), is important during vascular and cardiac surgeries. Unfractionated heparin is the most common anticoagulant used. The purpose of this analysis was to compare the i-STAT ACT (iACT) to the Hemochron ACT (hACT), both of which were then compared to anti-factor Xa (anti-Xa) assay, a representation of heparin level and activity. Prospective study. Tertiary care cardiovascular center. Eleven consecutive elective adult cardiac surgical patients. Prior to cardiopulmonary bypass, ACTs were measured using i-STAT and Hemochron technologies and compared to each other and to anti-Xa assay prior to and during a cumulative administration of heparin. Data were compared using bias analyses. Heparin (300 U/kg) was administered in quarterly doses. Coagulation labs were collected prior to and 3 minutes after each quarterly dose of heparin. The baseline ACTs for i-STAT and Hemochron were 147 and 142 seconds, respectively. A significant association was found between iACT and hACT (p = 0.002). The iACT measurements underestimated hACT at ACT levels >180 seconds or anti-Xa levels >0.75 U/mL. No significant difference was found between ACT data at anti-Xa levels <0.5 U/mL. There was a good association between the iACT and hACT; however, the 2 tests are not equivalent. Overall, the iACT underestimated the hACT. Agreement between the ACT technologies was good at lower ACTs and anti-Xa levels, but declined with an anti-Xa >0.75 U/mL.

Low molecular weight heparin for the prevention of severe preeclampsia: where next?

Low molecular weight heparin has been extensively evaluated for the prevention of preeclampsia in high-risk pregnant women; however, the results from these trials have been conflicting. This review discusses the potential mechanisms of action of low molecular weight heparin for the prevention of severe preeclampsia, how to optimize the selection of high-risk women for participation in future trials, and the importance of trial standardization.

Inactivated antithombin as anticoagulant reversal in a rat model of cardiopulmonary bypass: a potent and potentially safer alternative to protamine.

Heparin anticoagulation followed by protamine reversal is commonly used in cardiopulmonary bypass (CPB). As an alternative to protamine, a recombinant inactive antithrombin (riAT) was designed as an antidote to heparin and was previously shown to be as potent as protamine in-vitro. In the present study, riAT was assessed for its ability to neutralize heparin after CPB in a rat model. After 60min of CPB under heparin, rats received 5mg/kg protamine, 37.5mg/kg riAT or phosphate buffered saline (PBS) as placebo. Residual anticoagulant activity was assessed using the activated partial thromboplastin time assay before, and 10-30min after reversion. Haemodynamic monitoring was performed and plasma histamine concentration was also measured. In this model, riAT appeared to be as efficient as protamine in neutralizing heparin. Ten minutes after injection, riAT and protamine both decreased heparin activity, to 1.8±1.3 and 4.5±1.4u/ml, respectively (23.1±5.1u/ml in placebo group). Furthermore, evolution of mean carotid arterial pressure, heart rate and plasma histamine levels was comparable in rats treated with PBS or riAT, while protamine exhibited haemodynamic side effects and increased histamine plasma concentration. Thus, riAT could represent an advantage over protamine in CPB because it efficiently reverses heparin activity without negative effects on haemodynamic parameters and plasma histamine level.

Stability of Ceftazidime and Heparin in Four Different Types of Peritoneal Dialysis Solutions.

Intraperitoneal (IP) administration of ceftazidime is recommended for the treatment of peritoneal dialysis-associated peritonitis (PDAP) from Pseudomonas. Patients with PDAP may also need IP heparin to overcome problems with drainage of turbid peritoneal dialysis (PD) fluids and blockage of catheters with fibrin. Physico-chemical stability of ceftazidime and heparin, and biological stability of heparin in many types of PD solutions is unknown. Therefore, we investigated the stability of ceftazidime and heparin in 4 types of PD solutions. A total of 12 PD bags (3 for each type of solution) containing ceftazidime and heparin were prepared and stored at 4°C for 120 hours, and then at 25°C for 6 hours, and finally at 37°C for 12 hours. An aliquot was withdrawn after predefined time points and analyzed for the concentration of ceftazidime and heparin using high-performance liquid-chromatography (HPLC). Samples were assessed for pH, color changes, particle content, and anticoagulant activity of heparin. Ceftazidime and heparin retained more than 91% of their initial concentration when stored at 4°C for 120 hours followed by storage at 25°C for 6 hours and then at 37°C for 12 hours. Heparin retained more than 95% of its initial activity throughout the study period. Particle formation was not detected at any time under the storage conditions. The pH and color remained essentially unchanged throughout the study. Ceftazidime-heparin admixture retains its stability over long periods of storage at different temperatures, allowing its potential use for PDAP treatment in outpatient and remote settings.

Thromboelastography: a comparison of polybrene and heparinase for the inactivation of heparin

Thromboelastography: a comparison of polybrene and heparinase for the inactivation of heparin

Thrombodynamics, a new global coagulation test: Measurement of heparin efficiency

The actual coagulation status may be reliably measured using only highly sensitive global functional tests; however, they are not numerous and all of them have disadvantages. Thrombodynamics (TD), a novel global coagulation test, is sensitive to hypo- and hypercoagulable states. The main properties of this test were investigated, and its capabilities for hemostasis analysis were verified through pharmacodynamic monitoring of the most widely used anticoagulants, heparins. The anticoagulant effects in the plasma of donors (n = 20) and patients after hip replacement (n = 20) spiked with unfractionated heparin or enoxaparin were measured in vitro to eliminate the influence of pharmacokinetic factors. Sensitivity for heparins was compared for activated partial thromboplastin time, thrombin generation tests and TD. TD was shown to reliably characterize the pharmacodynamics of any heparin in the entire range of its prophylactic and therapeutic concentrations. Inter-individual variability for the anticoagulant action of heparins was also calculated using the TD data. This variability did not differ between the investigated groups and did not exceed 12% and 20% for the stationary clot growth rate in the presence of unfractionated heparin and enoxaparin, respectively. That finding was in accordance with the values determined earlier using the thrombin generation test. The study results showed that TD has advantages over the other global methods of coagulation analysis. These advantages are good standardization, high reproducibility, independence of the parameter values from patient age and gender, and a narrower parameter distribution in a normal population. These results indicate that TD is a promising universal assessment method that improves the quality of hemostasis analysis because it more reliably detects deviations from the parameters' reference values.

Invited commentary

In this translational study, Dr Dansdill and the group from Loyola show that the synthetic organic compound vepoloxamer (P-188) can potentiate the effects of heparin and tissue plasminogen activator in a rat model. This is a triblock, organic, synthetic, and amphipathic molecule that improves the rheology of blood. It has been studied in the sickle cell population with no reports of bleeding complications. To date, the use of anticoagulants to prevent thromboembolism and recurrent thrombosis in the arterial and venous circulation has been plagued by a very real and problematic attendant risk of bleeding. Whereas the advent of the direct oral anticoagulants has provided a breakthrough in convenience for the patient, the true “Holy Grail” of anticoagulant therapy is to establish a way to prevent pathologic thrombosis with minimal or no bleeding risk. Major bleeding rates for low-molecular-weight heparin approximate 2%, and even for the direct oral anticoagulants, major and clinically nonmajor bleeding may be as high as 8% to 10%.1Crowther M.A. Warkentin T.E. Bleeding risk and the management of bleeding complications in patients undergoing anticoagulant therapy: focus on new anticoagulant agents.Blood. 2008; 111: 4871-4879Crossref PubMed Scopus (225) Google Scholar, 2Yeh C.H. Gross P.L. Weitz J.I. Evolving use of new oral anticoagulants for treatment of venous thromboembolism.Blood. 2014; 124: 1020-1028Crossref PubMed Scopus (101) Google Scholar As such, this work represents a priority issue in anticoagulation pharmacology. If vepoloxamer allows a lower dose of heparin to be used and potentiation of tissue plasminogen activator, then the use of such a compound could have significant clinical impact and benefit. Importantly, this medication has been shown to be safe in phase I and II trials (albeit for different indications) and thus represents a tangible and realistic translation of bench research. Although this work is interesting and potentially important, areas that need to be clarified include the dose of heparin that was used and how it relates to clinical dosage (the amount of heparin in the current study seems to be low compared with what is clinically used in patients although previously used in other rat studies) and the establishment of parameters by which to monitor the effect of the drug with standard tests. Nonetheless, the data are provocative and the concept an important one. We should all applaud the efforts to look at improving the safety of patients by decreasing dosages of anticoagulants and fibrinolytic agents while maintaining therapeutic efficacy. The opinions or views expressed in this commentary are those of the authors and do not necessarily reflect the opinions or recommendations of the Journal of Vascular Surgery or the Society for Vascular Surgery. Synthetic, organic compound vepoloxamer (P-188) potentiates tissue plasminogen activatorJournal of Vascular SurgeryVol. 67Issue 1PreviewPoloxamer-188 is a synthetic, organic compound that acts by binding hydrophobic pockets on damaged lipid bilayers in the circulation. P-188 reduces blood viscosity and confers anti-inflammatory and cytoprotective effects. Vepoloxamer (Mast Therapeutics, San Diego, Calif) is a purified version of this compound that has limited side effects. The aim of this study was to investigate drug interactions between vepoloxamer and heparin and tissue plasminogen activator (tPA). Full-Text PDF Open Archive

Sustained Thromboresistant Bioactivity with Reduced Intimal Hyperplasia of Heparin-Bonded Polytetrafluoroethylene Propaten Graft in a Chronic Canine Femoral Artery Bypass Model

Bypass graft thrombosis remains a significant mode of failure in prosthetic graft revascularization. The purpose of this investigation was to evaluate the long-term thromboresistant effect of heparin-bonded expanded polytetrafluoroethylene (ePTFE) graft using Carmeda BioActive Surface technology in a canine model. Bilateral femorofemoral artery bypass grafts with ePTFE grafts were performed in 25 adult grayhound dogs. In each animal, a heparin-bonded ePTFE graft (Propaten, WL Gore) was placed on one side, whereas a control nonheparin graft was placed on the contralateral side. The graft patency was assessed at 1, 6, 12, 18, and 24months (n=5 per group) following the bypass. Heparin bioactivity of the graft material was analyzed. The effect of intimal hyperplasia was also assessed. All bypass grafts were patent at 1 month. Significantly greater patency rates were noted in the Propaten group compared to the control group at 12, 18, and 24months, which were 84%, 80%, and 80% vs. 55%, 35%, and 20%, respectively (P<0.02). There was a significant reduction in the anastomotic neointimal area and neointimal cell proliferation in Propaten grafts compared with control grafts at all groups between 6 and 24months (P<0.05). Heparin bioactivity as measured by antithrombin binding assay was demonstrated in the Propaten graft between 1 and 24months. Mean heparin activities on Propaten grafts ranged from 26.3±6.4 pmol/cm2 to 18.4±8.7 pmol/cm2 between 1 and 24months, which were significantly greater than the control group (P<0.001). Differences between mean heparin activities of explanted Propaten graft samples at the various time points were nonsignificant (P>0.05). Heparin-bonded ePTFE graft provides a thromboresistant surface and reduced anastomotic intimal hyperplasia at 2 years. The stable heparin bioactivity of the Propaten graft confers an advantage in long-term graft patency.

Monitoring of Heparin Activity in Live Rats Using Metal-Organic Framework Nanosheets as Peroxidase Mimics.

Metal-organic framework (MOF) nanosheets are a class of two-dimensional (2D) porous and crystalline materials that hold promise for catalysis and biodetection. Although 2D MOF nanosheets have been utilized for in vitro assays, ways of engineering them into diagnostic tools for live animals are much less explored. In this work, a series of MOF nanosheets are successfully engineered into a highly sensitive and selective diagnostic platform for in vivo monitoring of heparin (Hep) activity. The iron-porphyrin derivative is selected as a ligand to synthesize a series of archetypical MOF nanosheets with intrinsic heme-like catalytic sites, mimicking peroxidase. Hep-specific AG73 peptides as recognition motifs are physically adsorbed onto MOF nanosheets, blocking active sites from nonspecific substrate-catalyst interaction. Because of the highly specific interaction between Hep and AG73, the activity of AG73-MOF nanosheets is restored upon the binding of Hep, but not Hep analogues and other endogenous biomolecules. Furthermore, by taking advantages of biocompatibility and diagnostic property enabled by AG73-MOF nanosheets, the elimination process of Hep in live rats is quantitatively monitored by coupling with microdialysis technology. This work expands the biomedical applications of 2D MOF nanomaterials and provides access to a promising in vivo diagnostic platform.

Heparin Binding to an Engineered Virus-like Nanoparticle Antagonist.

The anticoagulant activity of heparin administered during medical interventions must be reversed to restore normal clotting, typically by titrating with protamine. Given the acute toxicity associated with protamine, we endeavored to generate safer heparin antagonists by engineering bacteriophage Qβ virus-like particles (VLPs) to display motifs that bind heparin. A particle bearing a single amino acid change from wild-type (T18R) was identified as a promising candidate for heparin antagonism. Surface potential maps generated through molecular modeling reveal that the T18R mutation adds synergistically to adjacent positive charges on the particle surface, resulting in a large solvent-accessible cationic region that is replicated 180 times over the capsid. Chromatography using a heparin-sepharose column confirmed a strong interaction between heparin and the T18R particle. Binding studies using fluorescein-labeled heparin (HepFL) resulted in a concentration-dependent change in fluorescence intensity, which could be perturbed by the addition of unlabeled heparin. Analysis of the fluorescence data yielded a dissociation constant of approximately 1 nM and a 1:1 binding stoichiometry for HepFL:VLP. Dynamic light scattering (DLS) experiments suggested that T18R forms discrete complexes with heparin when the VLP:heparin molar ratios are equivalent, and in vitro clotting assays confirmed the 1:1 binding stoichiometry as full antagonism of heparin is achieved. Biolayer interferometry and backscattering interferometry corroborated the strong interaction of T18R with heparin, yielding Kd ∼ 1-10 nM. These biophysical measurements further validated T18R, and VLPs in general, for potential clinical use as effective, nontoxic heparin antagonists.

Enzymatic Generation of Highly Anticoagulant Bovine Intestinal Heparin.

Unlike USP porcine heparin, bovine intestinal heparin (BIH) has a low anticoagulant activity. Treatment with 6-OST-1, -3, and/or 3-OST-1 afforded two remodeled heparins that met USP heparin activity and Mw specifications. We explored the pharmacodynamics and pharmacokinetics in a rabbit model. We conclude that a modest increase in the content of 3-O-sulfo groups in BIH increases the number of antithrombin III binding sites, making remodeled BIH behave similarly to pharmaceutical heparin.

Improving free-flap survival using intra-operative heparin: Ritualistic practice or evidence-base medicine? A systematic review

The failure rate of free flaps is approximately 5%, mostly due to thrombosis of microvascular anastomosis. A number of pharmacological agents have been tested in order to enhance the patency of microvascular anastomosis and so to as extend the survival of free flaps. One of them is heparin, a very commonly used anticoagulant. However, there exists no consensus on its use in microsurgery as concerns time of introduction (pre-, intra- or post-operative), recommended dosage, or duration of utilization. The aim of this study was to determine whether or not the use of intra-operative heparin, in its systemic or topical forms, can bring about improved survival of free flaps, and if and when it should be recommended in microsurgery. A systematic review on the PUBMED database enabled us to identify articles evaluating the benefits of intra-operative heparin with regard to free-flap survival. All in all, fifteen articles in animal and human research were selected. As far as animal research is concerned, 9 studies out of 11 showed the superiority of topical intra-operative heparin compared to saline in improving free-flap survival rates through improved patency of the anastomosis. As regards systemic intra-operative heparin, on the other hand, only two trials out of four yielded favorable results. In clinical research in humans, there has been no prospective randomized trial studying the action of topical intra-operative heparin in vessel irrigation of ex-vivo free flaps before vascular repermeabilisation. However, the preliminary results of four trials seem to provide positive arguments for this practice. The use of systemic per-operative heparin (intravenous injection) does not improve the survival of free flaps in either animal models or humans. In animal models, however, the use of topical intra-operative heparin (vessel irrigation) has been shown to improve the free-flap survival rate by avoiding thrombosis of microvascular anastomosis. Finally, in clinical studies concerning humans, as of now no prospective randomized trial has proven that use of topical intra-operative heparin to ensure vessel irrigation in ex-vivo flaps is likely to increase free-flap survival. Studies should be conducted to decide whether or not to validate a rather ritualistic practice that consists in irrigating the relevant vessels before anastomosis; does it or does it not improve the patency rate?

Quantitative analysis of antithrombin III binding site in low molecular weight heparins by exhausetive heparinases digestion and capillary electrophoresis.

The antithrombin III (ATIII)-binding site, which contains a special 3-O-sulfated, N-sulfated glucosamine residue with or without 6-O-sulfation, is mainly responsible for the anticoagulant activity of heparin. Undergoing the chemical depolymerization process, the preservation of the ATIII-binding site in low molecular weight heparins (LMWHs) are varied leading to the fluctuation of the anticoagulant activity. Herein we report a capillary electrophoresis (CE) method in combination with heparinase digestion and affinity chromatography for the measurement of molar percentage of ATIII-binding site of LMWHs. After exhaustively digesting LMWHs with the mixture of heparinase I, II and III, almost all the resulting oligosaccharide building blocks, including the three 3-O-sulfated tetrasaccharides derived from the ATIII-binding site, were resolved by CE separation. The peak area of each building block permits quantification of the molar percentage of the ATIII-binding site. The peaks corresponding to the 3-O-sulfated tetrasaccharides were assigned based on the linear relationship between the electrophoretic mobilities of the oligosaccharides and their charge to mass ratios. The peak assignment was further confirmed by analysis of the high ATIII affinity fractions, which contains much high 3-O-sulfated tetrasaccharides. With the method, the molar percentage of the ATIII-binding site of enoxaparin from different batches and different manufactures were measured and compared. It was demonstrated that the CE method provides more precise data for assessing the anti-FXa activity than that of the biochemical assay method.

Inhaled nebulised unfractionated heparin improves lung function in moderate to very severe COPD: A pilot study

BackgroundCOPD is an inflammatory airway disease characterised by progressive airflow limitation and air trapping, leading to lung hyperinflation and exercise limitation. Acute worsening of symptoms, including dyspnea, cough and sputum production, occurs during exacerbations which are associated with significantly reduced health related quality of life, and increased morbidity and mortality. Chronic bronchial mucus production and productive cough are risk factors for exacerbations. Medicines targeting bronchoconstriction and airway inflammation are the current mainstays of COPD therapy. However, there is growing concern with an increased risk of pneumonia in patients with COPD receiving regular inhaled corticosteroids and there is therefore a need to find safer alternative treatments.Previous studies have indicated that inhalation of unfractionated heparin (UFH) treats local inflammation, mucus hypersecretion and lung injury, without systemic anticoagulation, and is safe. Therefore, our primary objective was to demonstrate that inhaled UFH significantly improves lung function (FEV1) over 21 days of treatment in patients with COPD receiving pulmonary rehabilitation and that UFH provides a novel, safe and effective way of treating this complex disease. MethodsForty patients with moderate to very severe COPD admitted to the IRCCS San Raffaele Pisana Hospital for 21 days pulmonary rehabilitation were randomised to receive nebulised inhaled UFH (75,000 or 150,000 IU BID) or placebo for 21 days. All patients also received nebulised salbutamol (1 mg) and beclomethasone dipropionate (400 μg) BID over the same period.Lung function was measured at day 0, 7, 14 and 21 of treatment and at a follow-up visit 7 days post-treatment. Exercise capacity (6MWT) and dyspnoea (Borg score) were measured before and after treatment.In pre-clinical studies, the ability of basic proteins found in COPD sputum to neutralise the anticoagulant activity of heparin was determined using the AMAX heparin assay kit. Main resultsAt both doses, UFH significantly increased FVC following 7 days of treatment and 150,000 IU BID significantly increased FEV1 (+249 ± 69 ml compared with placebo) at this time, an effect maintained to the 28 day follow-up. Clinically significant improvement in exercise capacity and dyspnoea were seen after 21 days of treatment with both doses of UFH. There were no serious adverse events or effects on systemic coagulation. Pre-clinical studies demonstrated that the basic proteins lactoferrin, platelet factor-4 (PF-4), IL-8 and polyarginine, as a model of the eosinophil cationic protein (ECP), found in COPD sputum neutralise the anticoagulant activity of heparin. ConclusionInhaled nebulised UFH is safe and provides additional clinical benefit for patients with moderate to very severe COPD through effects that are independent of its anticoagulant activity.

Exploitation of a newly-identified entry pathway into the malaria parasite-infected erythrocyte to inhibit parasite egress

While many parasites develop within host cells to avoid antibody responses and to utilize host cytoplasmic resources, elaborate egress processes have evolved to minimize the time between escaping and invading the next cell. In human erythrocytes, malaria parasites perforate their enclosing erythrocyte membrane shortly before egress. Here, we show that these pores clearly function as an entry pathway into infected erythrocytes for compounds that inhibit parasite egress. The natural glycosaminoglycan heparin surprisingly inhibited malaria parasite egress, trapping merozoites within infected erythrocytes. Labeled heparin neither bound to nor translocated through the intact erythrocyte membrane during parasite development, but fluxed into erythrocytes at the last minute of the parasite lifecycle. This short encounter was sufficient to significantly inhibit parasite egress and dispersion. Heparin blocks egress by interacting with both the surface of intra-erythrocytic merozoites and the inner aspect of erythrocyte membranes, preventing the rupture of infected erythrocytes but not parasitophorous vacuoles, and independently interfering with merozoite disaggregation. Since this action of heparin recapitulates that of neutralizing antibodies, membrane perforation presents a brief opportunity for a new strategy to inhibit parasite egress and replication.

A Polymer Therapeutic Having Universal Heparin Reversal Activity: Molecular Design and Functional Mechanism.

Heparins are widely used to prevent blood clotting during surgeries and for the treatment of thrombosis. However, bleeding associated with heparin therapy is a concern. Protamine, the only approved antidote for unfractionated heparin (UFH) could cause adverse cardiovascular events. Here, we describe a unique molecular design used in the development of a synthetic dendritic polycation named as universal heparin reversal agent (UHRA), an antidote for all clinically used heparin anticoagulants. We elucidate the mechanistic basis for the selectivity of UHRA to heparins and its nontoxic nature. Isothermal titration calorimetry based binding studies of UHRAs having different methoxypolyethylene glycol (mPEG) brush structures with UFH as a function of solution conditions, including ionic strength, revealed that mPEG chains impose entropic penalty to the electrostatic binding. Binding studies confirm that, unlike protamine or N-UHRA (a truncated analogue of UHRA with no mPEG chains), the mPEG chains in UHRA avert nonspecific interactions with blood proteins and provide selectivity toward heparins through a combined steric repulsion and Donnan shielding effect (a balance of Fel and Fsteric). Clotting assays reveal that UHRA with mPEG chains did not adversely affect clotting, and neutralized UFH over a wide range of concentrations. Conversely, N-UHRA and protamine display intrinsic anticoagulant activity and showed a narrow concentration window for UFH neutralization. In addition, we found that mPEG chains regulate the size of antidote-UFH complexes, as revealed by atomic force microscopy and dynamic light scattering studies. UHRA molecules with mPEG chains formed smaller complexes with UFH, compared to N-UHRA and protamine. Finally, fluorescence and ELISA experiments show that UHRA disrupts antithrombin-UFH complexes to neutralize heparin's activity.

Synthetic heparin could improve blood-thinning treatments

A new synthetic version of the sulfated polysaccharide heparin that could be safer or have more-reversible activity than currently approved versions of the anticoagulant has been produced in quantities that begin to approach those needed for commercialization. Three types of heparins are currently approved as blood thinners to treat clotting disorders and prevent clotting in people undergoing kidney dialysis and surgery. Unfractionated heparin and low-molecular-weight heparin, derived from pig intestines, are mixtures with batch-to-batch inconsistencies, and contaminated batches have at times killed people. A synthetic heparin called fondaparinux is safer and homogeneous. But people taking heparin sometimes experience uncontrolled bleeding, and although a drug called protamine can reverse the anticoagulant activity of unfractionated heparin, it does so incompletely with low-molecular-weight heparin and doesn’t reverse fondaparinux activity at all. Robert J. Linhardt of Rensselaer Polytechnic Institute, Ji...

Population pharmacokinetics of human antithrombin concentrate in paediatric patients.

Antithrombin is increasingly used in paediatric patients, yet there are few age-specific pharmacokinetic data to guide dosing. We aimed to describe the pharmacokinetic profile of human (plasma-derived) antithrombin concentrate in paediatric patients. A 5-year retrospective review was performed of patients <19years of age admitted to our institution who received antithrombin concentrate, were not on mechanical circulatory support and had baseline (predose) and postdose plasma antithrombin activity levels available for analysis. Demographic and laboratory variables, antithrombin dosing information and data on the use of continuous infusion unfractionated heparin were collected. Population pharmacokinetic analysis was performed with bootstrap analysis. The model developed was tested against a validation dataset from a cohort of similar patients, and a predictive value was calculated. A total 184 patients met the study criteria {46.7% male, median age [years] 0.35 [interquartile range (IQR) 0.07-3.9]}. A median of two antithrombin doses (IQR 1-4) were given to patients (at a dose of 46.3 ± 13.6units kg-1 ), with median of three (IQR 2-7) postdose levels per patient. Continuous infusion unfractionated heparin was administered in 87.5% of patients, at a mean dose of 34.1 ± 22.7units kg-1 h-1 . A one-compartment exponential error model best fit the data, and significant covariates included allometrically scaled weight on clearance and volume of distribution, unfractionated heparin dose on clearance, and baseline antithrombin activity level on volume of distribution. The model resulted in a median -1.75% prediction error (IQR -11.75% to 6.5%) when applied to the validation dataset (n = 30). Antithrombin pharmacokinetics are significantly influenced by the concurrent use of unfractionated heparin and baseline antithrombin activity.

Precipitation and Neutralization of Heparin from Different Sources by Protamine Sulfate.

Current therapeutic unfractionated heparin available in Europe and US is of porcine mucosal origin. There is now interest, specifically in the US, to use bovine mucosa as an additional source for the production of heparin. The anticoagulant action of heparin can be neutralized by protamine sulfate, and in this study the ability of protamine to bind and neutralize the anticoagulant activities of heparin from porcine mucosa, bovine mucosa and bovine lung were assessed. Protamine sulfate was able to bind and precipitate similar amounts of heparins from different sources on a mass basis. However, differential amounts of anticoagulant activities were neutralized by protamine sulfate, with neutralization of porcine mucosa more effective than for bovine lung and bovine mucosa. For all heparins, potentiation of thrombin inhibition by antithrombin and heparin cofactor II was preferentially neutralized over antithrombin-mediated inhibition of factor Xa or plasma clotting time. Whole blood thromboelastography showed that neutralization by protamine sulfate was more effective than the antithrombin dependent thrombin inhibition assays indicated. While there was no absolute correlation between average or peak molecular weight of heparin samples and neutralization of anticoagulant activity, correlation was observed between proportions of material with high affinity to antithrombin, specific activities and neutralization of activity.

Precipitation of Heparin Products With Calcium Gluconate: The Activity of Inactive Ingredients.

Precipitation of Heparin Products With Calcium Gluconate: The Activity of Inactive Ingredients.