Measurement of Low Molecular Weight Heparin Ex Vivo Activities in Clinical Laboratories Using Various Anti-Xa Assays: Interlaboratory Variability and Requirement for an Agreed Low Molecular Weight Heparin Standard

1987 ◽  
Vol 58 (03) ◽  
pp. 879-883 ◽  
Author(s):  
P Sié ◽  
M F Aillaud ◽  
D de Prost ◽  
C Droullé ◽  
F Forestier ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Ex Vivo ◽  
Collaborative Study ◽  
Factor Xa ◽  
Low Molecular Weight ◽  
Low Molecular Weight Heparins ◽  
Clinical Laboratories ◽  
Interlaboratory Variability ◽  
Factor Xa Inhibition

SummaryThe only sensitive and convenient assay to assess the biological activity of low molecular weight heparins (LMWHs) is based on the potentiation of activated factor Xa inhibition. Several procedures for measuring the socalled anti Xa activity have been proposed. In this collaborative study including eight laboratories, we have used four different assays (three amidolytic and one clotting based methods) for measuring the anti Xa activity of ex vivo samples obtained after injecting three different LMWHs. The dispersion of the results obtained by calibration against standard heparin could be reduced by using any of the three LMWHs for calibration. A coefficient of variation less than 0.20 between values obtained in different laboratories using a variety of methods seems acceptable. However it is necessary to refer to a common international standard for expressing the results in units and to define, for each of the three products, the therapeutic range.

scholarly journals The anti-factor Xa range for low molecular weight heparin thromboprophylaxis

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Matthew Y. Wei ◽  
Salena M. Ward
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Dose Adjustment ◽  
Factor Xa ◽  
Research Data ◽  
Target Range ◽  
Low Molecular Weight ◽  
Low Molecular Weight Heparins ◽  
Therapeutic Doses ◽  
Venous Thromboses

Low molecular weight heparins (LMWHs) are now the mainstay option in the prevention and treatment of venous thromboembolism. In some patients receiving therapeutic doses of LMWH, activity can be measured by quantifying the presence of Anti-factor Xa (AFXa) for dose adjustment. However, currently there are no guidelines for LMWH monitoring in patients on thromboprophylactic, doses, despite certain patient populations may be at risk of suboptimal dosing. This review found that while the AFXa ranges for therapeutic levels of LMWHs are relatively well defined in the literature, prophylactic ranges are much less clear, thus making it difficult to interpret current research data. From the studies published to date, we concluded that a reasonable AFXa target range for LMWH deep venous thromboses prophylaxis might be 0.2-0.5 IU/mL.

SUBCUTANEOUS PHARMACOKINETICS/PHARMACODYNAMICS OF A LOW MOLECULAR WEIGHT DERIVATIVE (RD 11885) AND UNFRACTIONATED HEPARIN (PM 16885) IN PRIMATES

1987 ◽  
Author(s):  
R Norm ◽  
J Fareed ◽  
I Silber ◽  
A Belo ◽  
R Fenchel ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Unfractionated Heparin ◽  
Low Molecular Weight Heparin ◽  
Bleeding Time ◽  
Ex Vivo ◽  
Factor Xa ◽  
Repeated Administration ◽  
Treated Group ◽  
Low Molecular Weight ◽  
Thrombin Time

Subcutaneous pharmacokinetics/pharmacodynamics of a depolymerized low molecular weight heparin (RD 11885) and an unfractionated porcine mucosal heparin (PM 16885) were studied in primates (Macaca mulatta) at 0.5, 1.0 and 2.5 mg/kg/24 hr for 10 days after repeated administration. Ex vivo actions were determined using partial thromboplastin time (APTT), thrombin time (TT), IieptestR time (HT) , anti-factor Xa and anti-factor Ila assays at various time periods. Platelet counts and bleeding times were also measured. The cumulative bioavailability of RD 11885 calculated ex vivo was found to be 2-3 fold higher than PM 16885. The RD 11885 treated group exhibited a clear dissociation of the anti-factor Xa and anti-factor Ila activities. The biological half-life of RD 11885 was significantly greater than PM 16885 in all assays. No staircasing phenomenon was observed with either agent. A desensitization of the PM 16885 effects was observed. Neither agent produced any effect on the bleeding time or platelet count at any time. The pharmacokinetics/pharmacodynamics of RD 11885 were uniform and allowed the calculation of various pharmacologic parameters, whereas inconsistent results were obtained with PM 16885. These results demonstrate that this low molecular weight heparin exhibits better and more predictable bioavailability, in contrast to unfractionated heparin.

COMPARATIVE CLINICAL PHARMACOLOGY OF LOW MOLECULAR WEIGHT HEPARINS IN MAN

1987 ◽  
Author(s):  
Y Ordu ◽  
J Augustin ◽  
E V Hodenberg ◽  
V Bode ◽  
J Harenberg
Keyword(s):  
Molecular Weight ◽  
Clinical Pharmacology ◽  
Ex Vivo ◽  
Average Molecular Weight ◽  
Factor Xa ◽  
Low Molecular Weight ◽  
Pharmacological Properties ◽  
Clotting Time ◽  
Activity Time ◽  
Low Molecular Weight Heparins

Low molecular weight (LMW) heparins are obtained by diffent chemical procedures from conventional pig intestinal mucosa heparin. The LMW heparins differ in their molecular weight distribution and physicochemical properties. Therefore, we report of comparative studies on the anticoagulant and lipolytic effects of low molecular weight heparins in man.The following LMW heparins were used: BM 21-23 (Braun, Melsungen, FRG), CY 216 (Choay Laboratories, Paris, France), Heparin NM (Sandoz, Niimberg, FRG), Kabi 2165 (Kabi Vitrum AB, Stockholm, Sweden), RD Heparin (Hepar Industries, Franklin, US A), normal heparin (Braun). All heparins were administered intravenously and subcutaneously to six volunteers each.The data show considerable differences in the anticoagulant and lipolytic effects between the different low molecular weight heparins. From the area under the activity time curves (AUC) of the clotting assays for factor Xa (heptest), aPTT and thrombin clotting time the aXa/aPTT ratio ex vivo and aXa/alla ratio ex vivo were determined (table, average values)It can be seen that there are clear differences in the ex vivo ratios of the LMW heparins. There is a good correlation between the average molecular weight of the LMW heparins and the aXa/aPTT ratio after s.c. administration and of the aXa/alla ratio ex vivo after s.c. administration. Therefore, LMW heparins differ significantly in their clinical pharmacological properties.

An International Standard for Low Molecular Weight Heparin

1988 ◽  
Vol 60 (01) ◽  
pp. 001-007 ◽  
Author(s):  
T W Barrowcliffe ◽  
A D Curtis ◽  
E A Johnson ◽  
D P Thomas
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Collaborative Study ◽  
Low Molecular Weight ◽  
International Standard ◽  
Thrombin Inhibition ◽  
Interlaboratory Variability ◽  
Assay Methods ◽  
The Mean ◽  
International Collaborative Study

SummaryAn international collaborative study has been carried out with the aim of establishing an international standard for low molecular weight (LMW) heparin. Three preparations of LMW heparin were assayed against the International Standard for unfractionated heparin (UFH) by 25 laboratories in 13 countries, using nine different assay methods. The results confirmed previous findings of non-parallel assays, wide interlaboratory variability and differences between methods when LMW heparins are assayed against a UFH standard. Use of one of the LMW heparins as a standard for the other two gave parallel assays and much closer agreement between laboratories. The preparation in ampoules coded 85/600 was selected as likely to give the best agreement with the largest number of LMW heparins; potencies were assigned by taking the mean of all the anti-Xa assays, and the mean of the thrombin and APTT assays, to represent the two major groups of activities. Preparation 85/600 has been established by WHO as the 1st International Standard for LMW heparin, with potencies of 1,680 iu/ampoule by anti-Xa assays and 665 iu/ampoule by thrombin inhibition and APTT assays.

Pharmacological Properties of a Low Molecular Weight Butyryl Heparin Derivative (C4-CY 216) with Long Lasting Effects

1992 ◽  
Vol 67 (03) ◽  
pp. 346-351 ◽  
Author(s):  
S Saivin ◽  
M Petitou ◽  
J C Lormeau ◽  
D Dupouy ◽  
P Sié ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Specific Activity ◽  
Parent Compound ◽  
Factor Xa ◽  
Low Molecular Weight ◽  
Pharmacological Properties ◽  
Factor Xa Inhibition ◽  
Antifactor Xa ◽  
Heparin Derivative

SummaryWe have investigated the pharmacological properties of an O-acylated butyryl derivative of the low molecular weight heparin CY 216 (C4-CY 216). In a purified system the ability of C4-CY 216 to catalyze thrombin and factor Xa inhibition was comparable to that of CY 216. The antithrombin and antifactor Xa catalytic efficiencies of C4-CY 216 were reduced 217 and 12 times respectively when albumin (10 mg ml-1) was added to the reagents, while those of CY 216 were essentially unchanged. In plasma, the antifactor Xa specific activity of C4-CY 216 was close to that of CY 216 but the antithrombin specific activity was 2 times lower. After bolus and continuous intravenous injection to rabbits, the clearances of the two activities of C4-CY 216 were on average half the corresponding values of CY 216. After subcutaneous injection, the bioavailability of C4-CY 216 was comparable to that of CY 216. C4-CY 216 was as potent as CY 216 in preventing venous thrombosis in the thromboplastin-Wessler model and the duration of the antithrombotic effect was longer than that of the parent compound. The chemical alteration of CY 216 did not enhance the prohaemorrhagic effect in the rat tail transection model. Therefore, the new concept of heparin derivative having a low clearance and long lasting effects that we have recently reported for unfractionated heparin may also be applied to a low molecular weight heparin.

Studies in Man and Experimental Animals of a Low Molecular Weight Heparin Fraction

1981 ◽  
Vol 45 (03) ◽  
pp. 214-218 ◽  
Author(s):  
D P Thomas ◽  
R E Merton ◽  
W E Lewis ◽  
T W Barrowcliffe
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Specific Activity ◽  
Ex Vivo ◽  
High Specific Activity ◽  
Factor Xa ◽  
In Vivo Studies ◽  
Low Molecular Weight

SummaryIn vitro and in vivo studies were carried out on a commercially prepared low molecular weight heparin fraction. By APTT assay the fraction had a specific activity of half that of unfractionated mucosal heparin, yet retained full potency by anti-Xa assay (both clotting and chromogenic substrate). When administered intravenously to human volunteers, the anti-Xa/APTT ratio remained the same as it was in vitro. However, after subcutaneous injection, the ratio increased and anti-Xa activity could not be fully neutralized ex vivo by PF4. The fraction was as effective as unfractionated heparin in preventing experimental serum-induced thrombosis, suggesting that a heparin fraction with high specific activity by anti-Factor Xa assay compared to APTT activity may be an effective drug for the prophylaxis of venous thrombosis.

Markers of Hemostatic System Activation in Acute Deep Venous Thrombosis-Evolution during the First Days of Heparin Treatment

1993 ◽  
Vol 70 (06) ◽  
pp. 0909-0914 ◽  
Author(s):  
Keyword(s):  
Molecular Weight ◽  
Venous Thrombosis ◽  
Deep Venous Thrombosis ◽  
Unfractionated Heparin ◽  
Low Molecular Weight Heparin ◽  
Factor Xa ◽  
Low Molecular Weight ◽  
Dose Adaptation ◽  
Heparin Treatment ◽  
Lung Scan

SummaryFibrin D-Dimer (D-Di), prothrombin activation fragment (F 1+2) and thrombin-antithrombin III complexes (TAT) were measured using ELISA procedures in the plasma of patients with an acute deep venous thrombosis (DVT), at presentation and on days 2, 6 and 10 after initiation of heparin treatment. Patients were randomly allocated into two treatment groups: 44 patients received adapted doses of continuous intravenous unfractionated heparin (UH) whereas 47 received 1 mg/kg every twelve hours of a low molecular weight heparin (enoxaparin) subcutaneously. A phlebography and a perfusion lung scan were performed before inclusion and on day 10. Failure of therapy (n = 9) was defined by venogram worsening or confirmed pulmonary embolism. Improvement (n = 44) or stationary state (n = 38) were defined by venogram evolution in the absence of new leg scan defects.At presentation, D-Di, F 1 + 2 and TAT were above cut-off values in 97, 66 and 89% of patients respectively. D-Di levels correlated with the extent of venous thrombosis whereas TAT and F 1 + 2 did not. Mean levels of D-Di decreased sharply during the first days of treatment but were still abnormal on day 10. A secondary increase of D-Di on days 6 or 10 by more than 3 μg/ml occurred in 4 of the 9 patients who developed a thromboembolic recurrence but in none of the 72 patients who had a more favorable outcome. F 1 + 2 and TAT time-courses were not related to clinical evolution. In the Enoxaparin group, there was no relationship between antifactor Xa activities and any biological markers. TAT and F 1 + 2 levels fell on day 2 and remained stable until day 10. In contrast, in the UH group, TAT and F 1 + 2 did not significantly decrease on day 2, probably due to a delay in dose adaptation, but they declined slowly until day 10.In conclusion, D-Di displays a higher sensitivity than F 1 + 2 or TAT for the diagnosis of D\T. D-Di, but not TAT or F 1 + 2, follow-up seems to be of potential value for early detection of recurrency. Hemostatic activation is controlled earlier by fixed doses of a low molecular weight heparin, irrespective of the plasma anti-factor Xa activities, than by unfractionated heparin at adapted doses.

Comparison of the Non-Specific Binding of Unfractionated Heparin and Low Molecular Weight Heparin (Enoxaparin) to Plasma Proteins

1993 ◽  
Vol 70 (04) ◽  
pp. 625-630 ◽  
Author(s):  
Edward Young ◽  
Benilde Cosmi ◽  
Jeffrey Weitz ◽  
Jack Hirsh
Keyword(s):  
Molecular Weight ◽  
Unfractionated Heparin ◽  
Plasma Proteins ◽  
Low Molecular Weight Heparin ◽  
Specific Binding ◽  
Anticoagulant Activity ◽  
Factor Xa ◽  
Low Molecular Weight ◽  
Heparin Binding ◽  
Fixed Amount

SummaryThe non-specific binding of anticoagulantly-active heparin to plasma proteins may influence its anticoagulant effect. We used low affinity heparin (LAH) essentially devoid of anti-factor Xa activity to investigate the extent and possible mechanism of this non-specific binding. The addition of excess LAH to platelet-poor plasma containing a fixed amount of unfractionated heparin doubled the anti-factor Xa activity presumably because it displaces anticoagulantly-active heparin from plasma proteins. Although dextran sulfates of varying molecular weights also increased the anti-factor Xa activity, less sulfated heparin-like polysaccharides had no effect. These findings suggest that the ability to displace active heparin from plasma protein binding sites is related to charge and may be independent of molecular size. In contrast to its effect in plasma containing unfractionated heparin, there was little augmentation in anti-factor Xa activity when LAH was added to plasma containing low molecular weight heparin (LMWH), indicating that LMWH binds less to plasma proteins than unfractionated heparin. This concept is supported by studies comparing the anticoagulant activity of unfractionated heparin and LMWH in plasma with that in buffer containing antithrombin III. The anti-factor Xa activity of unfractionated heparin was 2-fold less in plasma than in the purified system. In contrast, LMWH had identical anti-factor Xa activity in both plasma and buffer, respectively. These findings may be clinically relevant because the recovered anti-factor Xa activity of unfractionated heparin was 33% lower in plasma from patients with suspected venous thrombosis than in plasma from healthy volunteers. The reduced heparin recovery in patient plasma reflects increased heparin binding to plasma proteins because the addition of LAH augmented the anti-factor Xa activity. In contrast to unfractionated heparin, there was complete recovery of LMWH added to patient plasma and little increase of anti-factor Xa activity after the addition of LAH. These findings may explain why LMWH gives a more predictable dose response than unfractionated heparin.

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