Anticoagulant effects of a low molecular weight heparinoid (Org 10172) in human volunteers and haemodialysis patients

Org 10172, a low MW heparinoid derived from animal intestinal mucosal tissue, has a mean molecular weight of 6500 D and a specific activity of 8.0 anti-Xa U/mg. Its elimination half-life after i.v. administration is 18 hours. Six human volunteers received repeated single i.v. injections of 800 and 3200 anti-Xa units of Org 10172, 5000 IU heparin or placebo. Bleeding time, platelet count and plasma beta thromboglobulin were not affected by Org 10172 or heparin. Heparin stimulated ADP-induced platelet aggregation (0.2 uM; p less than 0.05) and inhibited thrombin induced aggregation (0.3 U/ml; p less than 0.05), while the heparinoid lacked these effects. Heparin increased plasma platelet factor 4, whereas Org 10172 had no effect. In contrast to heparin Org 10172 had only a minor effect on the activated partial thromboplastin time and thrombin time, while both compounds induced anti-Xa activity in plasma. In a crossover study in six haemodialysis patients, both heparin and Org 10172 (34.4 and 22.4 anti-Xa units/kg/body weight) successfully prevented clotting of the extracorporeal circuit. Microscopical analysis of the artificial kidney membranes showed that the 34.4 unit Org 10172 dosage was as effective as heparin in preventing fibrin deposition. The haemostatic and coagulation effects were as expected from those observed in the volunteers except that there was a slower elimination of the plasma anti-Xa response. In addition heparin and Org 10172 (34.4 anti-Xa units/kg) inhibited the Xa-induced platelet aggregation (0.5 U/ml; p less than 0.01 and p less than 0.001 respectively).     

The influence of Org 10172, an antithrombotic heparinoid, on urinary blood loss after transurethral prostatectomy

We have measured the effects of Org 10172 (a mixture of naturally occurring glycosaminoglycans derived from hog intestinal mucosa) on blood loss after transurethral prostatectomy (TURP), using doses which are likely to prevent postoperative venous thrombosis (VT). 48 patients entered a double-blind randomised pilot study: 18 were given subcutaneous (sc) injections of a placebo and 30 received sc Org 10172 (750 anti-Xa units/day, 500 units twice daily (bid), or 750 units bid, starting just before TURP and continued until discharge; 10 patients per group). No Org 10172 regimen increased peroperative blood loss but all caused a similar trend towards increased urinary bleeding after surgery. Since there was no apparent dose effect gradient, it was decided to pool the data from all three dosing blocks: this analysis showed that Org 10172 increased geometric mean blood loss during the first 2 days after surgery from 10.4 gm hemoglobin (Hgb; range = 3.2-71) to 20.5 gm Hgb (range = 1.9-147) (p = .005), an effect which retained its significance after allowing for two other major determinants of postoperative bleeding, the weight of prostate resected and the length of surgery, and also when pooling was restricted to the twice daily Org 10172 injection groups and their corresponding controls. Bleeding was not severe, but our results indicate a need for caution when considering the use of Org 10172 in this setting.     

Interaction study between Org 10172, a low molecular weight heparinoid, and acetylsalicylic acid in healthy male volunteers.

Potential interactions between Org 10172 (Lomoparan, i.v. bolus injection of 3,250 anti-Xa units followed by 750 units twice daily s.c. for 8 days) and acetylsalicylic acid (ASA) (500 mg orally 14 and 2 h before i.v. Org 10172 administration) were studied in eight healthy male volunteers using an open, randomised three-way cross-over design. Except for moderate bruising at venepuncture and s.c. injection sites which were equally distributed over all three treatments (Org 10172 alone, ASA alone, Org 10172 and ASA combined), no side effects were observed. The effects of the separate drugs on several haemostatic parameters were as expected, although the prolongations in bleeding time after ASA were highly variable and tended to be somewhat more pronounced after the combination (p greater than 0.05). Org 10172 did not influence the inhibiting effects of ASA on platelet function nor the functional recovery afterwards, as evaluated by thromboxane A2 (TXA2) generation and collagen-induced platelet aggregation. Furthermore, no important interactions were observed with regard to the coagulation tests and plasma anti-Xa activity. Although this study did not entirely exclude small interactions between Org 10172 and ASA in this relatively small group of subjects, these effects are probably without clinical significance.     

Anticoagulant and antithrombotic effects of heparin and low molecular weight heparin fragments in rabbits

Heparin and heparin fragments of different molecular weight and with different anti-factor X_a/APTT activity ratios were studied with respect to their ability to inhibit thrombus formation in an animal model. It is concluded that: a) Neither anti-factor X_a nor the APTT activity alone is a good reflector of the antithrombotic activity. b) Anti-factor X_a active fragments must have a minimum molecular weight in order to elicit good antithrombotic activity. c) High affinity for antithrombin III is important for good antithrombotic activity. d) A heparin fragment of molecular weight 4 000 has the same antithrombotic activity as heparin but less effect on the clotting time.     

Signs of thrombin generation in pediatric cardiac catheterization with unfractionated heparin bolus or subcutaneous low molecular weight heparin for antithrombotic cover

Introduction: Thrombosis is one of the most frequent adverse events after cardiac catheterization, which can be reduced by anticoagulation with unfractionated heparin (UFH) in both children and adults. Low molecular weight heparin (LMWH) might possibly offer advantages. Laboratory signs of thrombin generation during pediatric cardiac catheterization, with unfractionated heparin (UFH) bolus or subcutaneous LMWH for thrombosis prophylaxis, were determined in a first step to investigate the potential of LMWH for antithrombotic cover. Materials and methods: Signs of thrombin generation (D-dimer and F₁₊₂), anti-Xa activity and activated clotting time (ACT) were measured in 65 patients with congenital heart disease. A total of 40 patients were treated with a UFH bolus of 100 IU/kg bodyweight and, in 25 children, enoxaparin was subcutaneously administered at a dosage of 1/1.6 mg/kg bodyweight. Results: The dose to plasma activity of enoxaparin was more consistent than in the UFH group. Only a slight elevation of F₁₊₂ was found in some patients, which was a little higher in the enoxaparin group, but no difference of incidence of increased F₁₊₂ generation was detected between the two groups. D-dimer was elevated in three children after UFH bolus application, but no such effect was observed in any child after LMWH administration. Conclusions: Application of LMWH was equally efficacious during pediatric cardiac catheterization than UFH bolus administration, as determined by plasma levels and markers of clotting activation. In contrast to UFH bolus, no further monitoring was necessary after the application of LMWH during cardiac catheterization due to a consistent dose to plasma activity.     

Plasma lipolytic activity after subcutaneous administration of heparin and a low molecular weight heparin fragment

The effect of heparin and a low molecular weight heparin fragment (LMWH, mean molecular weight 4000-6000) on plasma anticoagulation and lipolysis was studied in eight healthy men. The activities of antifactor Xa (antiFXa), lipoprotein lipase (LPL), hepatic lipase (HL) and plasma levels of free fatty acids (FFA) were analysed after the injection of 5000 antiFXa units of heparin or LMWH subcutaneously. In comparison with heparin, the administration of LMWH resulted in a significantly higher antiFXa activity (p less than 0.001) but a lower release of LPL and HL (p less than 0.001), which did not increase plasma FFA. It is concluded that subcutaneous injection of LMWH in men elicits an adequate anticoagulant effect measured as antiFXa activity but has a negligible effect on plasma lipolytic activity.     

Pharmacokinetics of a low molecular weight heparin, Logiparin, after intravenous and subcutaneous administration to healthy volunteers

In six healthy volunteers we have estimated the pharmacokinetic parameters of the anti factor Xa (AXa) and anti factor IIa (AIIa) activities of a LMW heparin, Logiparin. For the AXa the following parameters were estimated in a 1-compartment model (mean and 95% confidence limits in brackets): elimination half life 82 minutes (60–127 min), absorption half life (s.c.inj.) 200 minutes (137–368 min), bioavailability 90% (24–156 %), and apparent volume of distribution 3.9 1 (3.1–5.2 1). The plasma activity was linearly correlated to the dose given and to the body weight of the volunteer. For the AIIa the parameters estimated in a 1-compartment model were: elimination half life 71 minutes (52–115 min), absorption half life 257 minutes (133–3442 min), bioavailability 67% (44–90 %), and apparent volume of distribution 10.1 1 (7.2–16.7 1). The plasma activity was dependent on dose and body weight but it also seemed to be influenced by individual factors. This study shows that the absorption rate is the rate limiting factor and the explanation for the long lasting effect of this LMW heparin after subcutaneous injection. The slow absorption rate and the high bioavailability are probably the major advantages of LMW heparins compared to conventional heparin.     

A comparison of the antithrombotic and haemorrhagic effects of a low molecular weight heparin (LHN-1) and conventional heparin

The antithrombotic effects after intravenous administration of a low molecular weight heparin (LHN-1) and conventional heparin were compared in a rabbit model of experimental thrombosis, where thrombus formation was induced by a combination of endothelial damage and stasis. Both compounds were able to prevent thrombosis completely. However, LHN-1 was significantly less potent than conventional heparin, the ratio between doses with the same antithrombotic effect being 2.4:1 on a weight basis. Bleeding times after administration of LHN-1 and conventional heparin were determined by tail transsection in anaesthetized rats and by template bleeding in the ear of conscious pigs. Given intravenously at a dose ratio of 2.4:1 (w/w), LHN-1 affected APTT less than conventional heparin, whereas the effects on haemostasis were not significantly different. In conclusion, it was found that after intravenous administration LHN-1 prevented experimental thrombosis as effectively as conventional heparin. However, the correlation between antithrombotic and haemorrhagic effects of LHN-1 was the same as that of conventional heparin. The corresponding relation in man remains to be determined.     

Influence of heparin and a low molecular weight heparinoid on specific endogenous and exogenous fibrinolytic factors during rest and exercise.

The effects of heparin (5,000 IU i.v.) and the low molecular weight heparinoid Org 10172 (Orgaran) (3,250 anti-Xa units i.v.) on components of the fibrinolytic system were studied in two double-blind, randomised, placebo-controlled, cross-over trials using healthy subjects. In study A (n = 6) the effects were studied during rest and standardized exercise and in study B (n = 6) during a low dose infusion of recombinant tissue-type plasminogen activator (rt-PA; 80 micrograms over 16 min). At rest, heparin and Org 10172 did not influence the plasma concentrations of endogenous t-PA antigen and activity, urokinase-type PA (u-PA) antigen, plasmin activatable pro-urokinase (scu-PA), active urokinase (tcu-PA) and plasminogen activator inhibitor-1 (PAI-1) antigen. Recombinant t-PA antigen and activity during rt-PA infusion were also not affected. During exercise, neither heparin nor Org 10172 influenced the area under the curve (AUC) of t-PA and u-PA antigen and t-PA activity when compared with placebo. Unexpectedly, after heparin the AUC of t-PA activity was 49% larger (range +19 to +245%) than after Org 10172 (p < 0.05). The last difference was considered spurious, scu-PA, tcu-PA and PAI-1 antigen levels at 2 min after termination of exercise were unaffected by both compounds (p > 0.05). Sulphated polysaccharides do not increase fibrinolytic activity of the plasma by changing the concentrations of the components of the fibrinolytic system.     

Fibrinolytic and anticoagulant activity after a single subcutaneous administration of a low dose of heparin or a low molecular weight heparin-dihydroergotamine combination

The anticoagulant and potential profibrinolytic effect of a combination of low molecular weight heparin with dihydroergotamine (LMWH-DHE) and of unfractionated heparin was studied in eight healthy volunteers. Each volunteer received a subcutaneous injection of either LMWH-DHE (1,500 U anti-Xa of LMWH + 0.5 mg DHE), unfractionated heparin (5,000 IU) or of placebo (saline) between 7 and 8 h in the morning on three different occasions. Anti-Xa activity, and fibrinolytic activity measured by the euglobulin clot lysis time (ECLT) and by the fibrin plate assay were determined before and at different times after administration of the three substances. Anti-Xa activity in plasma reached a maximum four hours after injection of both LMWH-DHE and unfractionated heparin. LMWH-DHE showed a better bioavailability when compared to unfractionated heparin; the anti-Xa activity peak was two and a half fold higher after LMWH-DHE despite injection of a three fold lower dose of anti-Xa units. The half-life of anti-Xa activity was approximately 4 hours for LMWH-DHE but only 90 min for unfractionated heparin. The fibrinolytic activity measured by ECLT as well as by fibrin plate assay, showed a significant increase during the day reaching a peak 8-12 h after injection regardless of the product administered (including the placebo). The profile of the diurnal fibrinolytic activity curve was identical for all three substances. The increase in fibrinolytic activity, observed after administration of LMWH-DHE or unfractionated heparin, was therefore not due to these drugs but reflected the circadian physiological fluctuation of fibrinolysis.     

The relative antithrombotic effectiveness of heparin, a low molecular weight heparin, and a pentasaccharide fragment in an animal model

The antithrombotic efficacy of unfractionated heparin (UFH), a low molecular weight heparin (LMWH) and a synthetic pentasaccharide (PENTA) has been compared in an animal model for stasis thrombosis. We have also compared the relative ability of these three agents to impair thrombin generation in vitro and in vivo, and measured their effects on anti-Xa activity and thrombin clotting times. UFH, LMWH and PENTA all had the capacity to impair thrombogenesis, although there were marked differences in their relative effectiveness. Reduction of thrombin generation to 20% of control values was closely correlated with the prevention of thrombosis after 20 minutes' stasis, but this was only achieved with UFH. The same dry weight dose of LMWH or PENTA reduced thrombin generation to about half control values, and neither significantly impaired thrombus formation after 20 minutes' stasis. Impaired thrombin generation correlated better than anti-Xa activity with prevention of stasis thrombosis. In this model, UFH was clearly superior to LMWH and PENTA as an antithrombotic agent.     

Heparin and fibrinolysis--comparison of subcutaneous administration of unfractionated and low molecular weight heparin

The effects on the fibrinolytic system after a single s.c. bolus injection (at 9 a.m.) of either 5000 IU conventional heparin or 5000 anti-Xa U of a fractionated low molecular weight heparin (Fragmin, KabiVitrum, Sweden) were investigated in 9 healthy volunteers. The effects were compared to those of an injection of normal saline in 6 volunteers. Samples for biochemical analyses were taken regularily during 6 hours after drug or placebo administration. In the coagulation system the following parameters were measured: Activated partial thromboplastin time (APTT), anti-Xa activity, thrombin time and fibrinogen. The fibrinolytic system was monitored by analysing: plasminogen, alpha 2-antiplasmin, fibrin(ogen) degradation products (FDP), euglobulin clot lysis time (ECLT), tissue plasminogen activator (t-PA) activity, t-PA antigen and plasminogen activator inhibitor (PAI) activity. Injection of the 2 drugs was followed by elevations in APTT and anti-Xa activity, and were more pronounced for Fragmin than heparin. The fibrinolytic system exhibited a diurnal variation with decreasing PAI activity and increasing t-PA activity during the day. Volunteers receiving normal saline (placebo) showed a similar pattern. The results were unrelated to heparin. It is concluded from this study that neither heparin nor Fragmin had any significant effect on the fibrinolytic parameters when measured after a single s.c. bolus injection since the observed variations were within the diurnal range.     

The effects of heparin and low molecular weight heparins on bone

Recent clinical trials have shown that the risk of developing osteoporosis is substantially lower when low molecular weight heparins (LMWHs) are used in place of unfractionated heparin. While the reason(s) for this difference has not been fully elucidated, studies with animals have suggested that heparin causes bone loss by both decreasing bone formation and increasing bone resorption. In contrast, LMWHs appear to cause less bone loss because they only decrease bone formation. Whether all LMWHs decrease bone formation and therefore cause bone loss is unknown. For example, preliminary in vitro studies with the synthetic pentasaccaride, Fondaparinux, have suggested that it may not decrease bone formation and thus, may have no deleterious effects on bone. Further studies are required in order to determine if all LMWHs cause bone loss equally.     

Anticoagulant and lipolytic effects of a low molecular weight heparin fraction

The lipolytic and anticoagulant actions of a 4000 dalton low molecular weight (LMW) heparin were compared with unfractionated mucosal heparin after intravenous and various subcutaneous doses in man. I.v. injection of 100 USP units/kg body weight lipoprotein lipase (LPL) activity, and inhibition of factor Xa decreased with a half life twice as long after LMW heparin compared to normal heparin (p < 0.05). There were no differences in half lives for HTGL activity, thrombin inhibition and on aPTT. The area under the activity time curve (AUC) of LPL and factor Xa was double with LMW heparin (p < 0.05). S.c. administration showed that the AUC of LMW heparin on the factor Xa inhibition was 10 times larger compared to normal heparin. LPL activity was released comparable to normal heparin. The effects on HTGL were three times larger compared to normal heparin. There were no differences in half lives. The data show that in contrast to normal heparin LMW heparin is rapidly and completely absorbed from the subcutaneous depots. The pharmacodynamic data of LPL activity and factor Xa inhibition suggest similar release mechanisms.     

Effects of low molecular weight heparin and unfragmented heparin on induction of osteoporosis in rats

A comparison between the effect of low molecular weight heparin (LMWH) and unfragmented heparin (UH) on induction of osteoporosis was made in 60 rats treated with either UH (2 IU/g bw), LMWH in 2 doses (2 XaI U/g or 0.4 XaI U/g) or placebo (saline) for 34 days. Studied variables were: bone mineral mass in femora; fragility of humera; zinc and calcium levels in serum and bone ash and albumin in plasma. A significant reduction in bone mineral mass was found in all heparin-treated rats. There was no difference between UH and LMWH in this respect. The effect was dose-dependent in LMWH-treated animals. The zinc contents in bone ash were decreased in all heparin-treated rats as compared with controls. No recognizable pattern was seen in alterations of zinc or calcium in serum. The fragility of the humera, tested as breaking strength did not differ between treatment groups and controls. In conclusion, if dosed according to similar factor Xa inhibitory activities, LMWH induces osteoporosis to the same extent as UH and in a dose-dependent manner. The zinc content in bone ash was decreased after heparin treatment, irrespective of type of heparin given.     

Differential effects of heparin and low molecular weight heparin on osteoblastogenesis and adipogenesis in vitro

We have previously demonstrated that heparin produces cancellous bone loss in rats due in part to a decrease in the number of osteoblasts lining the trabecular bone surface. In the present study, we use a stromal-derived cell culture system together with measurements of alkaline phosphatase (ALP) activity, to compare the effects of heparin and the low molecular weight heparin (LMWH), Fragmin, on osteoblast differentiation in vitro. In addition, we examined the possibility that both heparin and LMWH can induce adipogenesis in our stromal cell culture system. Both heparin and LMWH were found to produce a statistically significant (P < 0.01) and concentration-dependent decrease in the number of osteoblasts while increasing the number of adipocytes. When the effects of gravimetrically equivalent amounts of heparin and LMWH were compared, heparin had a 4-fold greater effect than LMWH. In contrast to heparin, N-desulfated heparin was found to have minimal effects on both osteoblast and adipocyte differentiation indicating that the heparin effect is not only chain-length dependent but also charge-dependent. The observation that LMWH has less of an effect on bone formation than heparin is compatible with the results of clinical trials indicating that LMWH produces less bone loss after long-term administration.     

Antithrombotic effects of DX-9065a,a direct factor Xa inhibitor: a comparative study in humans versus low molecular weight heparin

BACKGROUND: Recent evidence suggests that TF may play a causal role in acute coronary syndromes, and may be an important therapeutic target. Several inhibitors of TF, coagulation factors VIIa and Xa are under investigation as novel antithrombotic approaches. We compared the antithrombotic effects of DX-9065a, a new FXa inhibitor, vs. enoxaparin. METHODS AND RESULTS: The protocol was an open-label crossover study. Subjects (n = 6) participated in 3 consecutive study-arms: a) enoxaparin + ASA (1 mg/Kg s. c + 162 mg/day x 3 days), b) three escalating doses of DX-9065a (1 mg bolus + 0.25 mg/h x 2 h, followed by an additional 1 mg bolus + 0.625 mg/h x 2 h and, a final 1 mg bolus + 1.25 mg/h x 2 h), and c) the same doses of DX-9065a in Arm 2 plus ASA pre-treatment. The antithrombotic effects were assessed using the Badimon perfusion chamber at each dose level. The administration of DX-9065a whether alone or combined with ASA significantly inhibited thrombus formation at high and low shear rate conditions while enoxaparin did not have a significant effect. Furthermore, these antithrombotic effects were obtained without significant prolongations of the standard coagulation parameters as those induced by enoxaparin. CONCLUSIONS: The direct inhibition of FXa by DX-9065a appears to be a safe and effective new approach for preventing the thrombotic complications of atherosclerotic disease. The clinical effectiveness of the direct FXa inhibitors should be further investigated.     

Human pharmacological studies of a defined low molecular weight heparin fraction (Fragminr) evidence for a simultaneous inhibition of factor Xa and IIa (thrombin)

The effect of a low molecular weight heparin (FragminR) (20–80 U/kg) was studied in 10 healthy male volunteers after intravenous administration. Clotting ab-abnormalities are extensive shortly after injection, lasting for 1 – 2 hours depending on heparin dosage. Dilute thrombin time, showing a close correlation to anti-F-Xa activity, is as sensitive as anti-F-Xa. The parallel time course of dilute thrombin time and anti-F-Xa activity clearly demonstrates that LMWH has an effect on F-IIa lasting as long as that of F-Xa. After subcutaneous administration clotting abnormalities are only slight with 40–60 U/kg, in contrast to the intravenous study. The platelet system remains unchanged.