Large inter-individual variation of the pharmacodynamic effect of anticoagulant drugs on thrombin generation.

Anticoagulation by a standard dosage of an inhibitor of thrombin generation presupposes predictable pharmacokinetics and pharmacodynamics of the anticoagulant. We determined the inter-individual variation of the effect on thrombin generation of a fixed concentration of direct and antithrombin-mediated inhibitors of thrombin and factor Xa. Thrombin generation was determined by calibrated automated thrombinography in platelet-poor plasma from 44 apparently healthy subjects which was spiked with fixed concentrations of otamixaban, melagatran, unfractionated heparin, dermatan sulfate and pentasaccharide. The variability of the inhibitory effect of the different anticoagulants within the population was determined using the coefficient of variation, i.e. the standard deviation expressed as a percentage of the mean. The inter-individual coefficients of variation of the endogenous thrombin potential and peak height before inhibition were 18% and 16%, respectively and became 20%-24% and 24%-43% after inhibition. The average inhibition of endogenous thrombin potential and peak height (ETP, peak) brought about by the anticoagulants was respectively: otamixaban (27%, 83%), melagatran (56%, 63%), unfractionated heparin (43%, 58%), dermatan sulfate (68%, 57%) and pentasaccharide (25%, 67%). This study demonstrates that the addition of a fixed concentration of any type of anticoagulant tested causes an inhibition that is highly variable from one individual to another. In this respect there is no difference between direct inhibitors of thrombin and factor Xa and heparin(-like) inhibitors acting on the same factors.

Danaparoid sodium reduces ischemia/reperfusion-induced liver injury in rats by attenuating inflammatory responses.

This study was undertaken to examine the mechanism by which danaparoid sodium (DS), a heparinoid that contains mainly heparan sulfate, prevents reperfusion-induced hepatic damage in a rat model of ischemia/reperfusion (I/R)-induced liver injury. Administration of DS significantly reduced liver injury and inhibited the decrease in hepatic tissue blood flow in rats. DS attenuated hepatic I/R-induced increases in hepatic tissue levels of tumor necrosis factor (TNF) and myeloperoxidase (MPO) in vivo. In contrast, neither monocytic TNF production nor neutrophil activation was inhibited by DS in vitro. DS enhanced I/R-induced increases in levels of calcitonin-gene related peptide (CGRP), a neuropeptide released from sensory neurons, and of 6-ketoprostaglandin (PG) F (1a) , a stable metabolite of PGI (2) , in liver tissues. The therapeutic effects of DS were not seen in animals pretreated with capsazepine, an inhibitor of sensory neuron activation. The distribution of heparan sulfate in the perivascular area was significantly increased by DS administration in this rat model. DS significantly increased CGRP release from isolated rat dorsal root ganglion neurons (DRG) in vitro, while DX-9065a, a selective inhibitor of activated factor X, did not. DS enhanced anandamide-induced CGRP release from DRG in vitro. These observations strongly suggested that DS might reduce I/R-induced liver injury in rats by attenuating inflammatory responses. These therapeutic effects of DS might be at least partly explained by its enhancement of sensory neuron activation, leading to the increase the endothelial production of PGI (2) .

Antithrombotic activity of dermatan sulfate in heparin cofactor II-deficient mice.

Heparin cofactor II (HCII) is a plasma protein that inhibits thrombin rapidly in the presence of dermatan sulfate or heparin. We previously reported that the time to thrombotic occlusion of the carotid artery after photochemical injury was shorter in HCII-deficient mice than in wild-type control animals. In this paper, we describe the antithrombotic activity of dermatan sulfate in wild-type and HCII-deficient mice. Intravenous administration of porcine skin dermatan sulfate induced a dose-dependent prolongation of the carotid artery occlusion time in HCII(+/+) mice that was not observed in HCII(-/-) animals. Pharmacokinetic studies suggested that porcine skin dermatan sulfate expresses antithrombotic activity after being transferred from the plasma to sites in the vessel wall. Using invertebrate dermatan sulfate preparations, we showed that N-acetylgalactosamine-4-O-sulfate residues are required for the HCII-dependent antithrombotic effect. Furthermore, the invertebrate dermatan sulfates, which have higher charge densities than mammalian dermatan sulfate, slightly prolonged the thrombotic occlusion time of HCII(-/-) mice. These results indicate that HCII mediates the antithrombotic effect of porcine skin dermatan sulfate after injury to the carotid arterial endothelium in mice, whereas more highly charged dermatan sulfates possess weak antithrombotic activity independent of HCII.

Danaparoid: a review of its use in thromboembolic and coagulation disorders.

UNLABELLED: Danaparoid (danaparoid sodium) is a low molecular weight heparinoid which has undergone clinical study for use as continued anticoagulant therapy in patients with heparin-induced thrombocytopenia (HIT), for the prophylaxis and treatment of deep vein thrombosis (DVT), and for the treatment of disseminated intravascular coagulation (DIC). A nonblind study in patients with HIT has reported that complete clinical resolution is significantly more likely in patients receiving danaparoid than in patients receiving dextran 70. In addition, retrospective analyses and noncomparative data support the use of danaparoid for continued anticoagulant therapy in patients with HIT. Studies in patients undergoing hip surgery have shown that danaparoid significantly reduces the incidence of postoperative DVT compared with aspirin, warfarin, dextran 70 and heparin-dihydroergotamine, while additional data suggest no difference between danaparoid, enoxaparin and dalteparin. In patients undergoing abdominal or thoracic surgery for removal of a malignancy, danaparoid reduced the incidence of postoperative DVT compared with placebo, but showed no significant difference when compared with unfractionated heparin (UFH). Two studies have compared danaparoid with UFH in the prophylaxis of DVT following acute ischaemic stroke; twice daily danaparoid was significantly superior to UFH whereas there was no significant difference between a once-daily dosage and UFH. Danaparoid did not differ from UFH in terms of efficacy in the treatment of existing DVT. In all comparative studies examining the efficacy of danaparoid in the prophylaxis or treatment of DVT (versus warfarin, dextran 70, enoxaparin, dalteparin, aspirin, heparin-dihydroergotamine, UFH and placebo), the incidence of haemorrhagic complications did not differ between treatment groups. In patients with DIC, 61.9% of those patients receiving danaparoid experienced either disappearance or reduction of symptoms of DIC whereas 62% of those receiving UFH showed either no change or aggravation of their symptoms. There was no significant difference between treatment groups in tolerability or overall improvement of DIC. CONCLUSIONS: Danaparoid is an effective anticoagulant agent which has undergone clinical evaluation in a wide range of disease indications. Current guidelines support the use of danaparoid in prophylaxis of DVT following ischaemic stroke, and in patients who develop HIT. Danaparoid has shown efficacy in DIC, and for DVT prophylaxis in patients undergoing hip surgery although further data are required to establish the role of danaparoid in these indications. In particular, double-blind trials comparing danaparoid with such recommended therapies as the low molecular weight heparins will provide more definitive data on the place of danaparoid in the clinical management of these conditions and ultimately lead to improved patient outcomes.

Pharmacokinetic studies of dalteparin (Fragmin), enoxaparin (Clexane), and danaparoid sodium (Orgaran) in stable chronic hemodialysis patients.

BACKGROUND: Low molecular weight heparins (LMWHs) and danaparoid are an alternative to unfractionated heparin (UH) for anticoagulation during hemodialysis. Few data are available concerning their duration of action and whether drug accumulation occurs with continued use. We performed a prospective randomized study of the pharmacokinetics of dalteparin and enoxaparin plus danaparoid in 21 hemodialysis patients. METHODS: Patients were randomly assigned to administration of enoxaparin, 40 mg; dalteparin, 2,500 U; or danaparoid, 34 U/kg, for 4 weeks. Antifactor Xa levels were measured at the end of weeks 1 and 4 immediately before the injection and at prescribed intervals up to 48 hours postinjection. RESULTS: No bleeding or thrombotic episodes occurred during the study. Mean antifactor Xa activities 4 hours postinjection were 0.2 +/- 0.035 (SEM), 0.38 +/- 0.028, and 0.54 +/- 0.051 U/mL week 1 and 0.26 +/- 0.038, 0.40 +/- 0.055, and 0.64 +/- 0.050 U/mL week 4 for dalteparin, enoxaparin, and danaparoid, respectively. Both weeks 1 and 4, antifactor Xa activity 3 hours postdose was significantly greater for danaparoid sodium compared with enoxaparin and dalteparin. There were no significant differences between antifactor Xa activity week 4 versus week 1 for enoxaparin and dalteparin; however, danaparoid sodium levels during dialysis were significantly greater after 4 weeks of treatment (P = 0.0328, 1 hour; P = 0.003, 2 hours; P = 0.0128, 3 and 4 hours). CONCLUSION: Dalteparin and enoxaparin provide adequate anticoagulation for hemodialysis using single bolus injections at relatively low doses. Danaparoid sodium at the current recommended dosage resulted in greater anticoagulation than enoxaparin or dalteparin and may have an

Low-molecular-weight heparin and dermatan sulfate end group-labeled with tyramine and fluorescein. Biochemical and biological characterization of the fluorescent-labeled heparin derivative.

To improve the understanding of the biological functions and pharmacology of heparin and dermatan sulfate, low-molecular-weight heparin (LMWH) and low-molecular-weight dermatan sulfate (LMWDS) were labeled with tyramine (T) by covalently linking T to the terminal residue of 2,5-anhydromannose (or 2,5-anhydrotalose for dermatan sulfate). The covalent labeling was demonstrated by nuclear magnetic resonance spectroscopy. The tyramine-labeled LMWH (LMWH-T) was also labeled with fluorescein (F) by further reacting it with fluorescein isothiocyanate. The fluoresceinated LMWH-T (LMWH-T,F ) was used to analyze biological functions on blood coagulation and binding to leukocytes. The biological activities on factor Xa and thrombin inhibition remained unchanged compared with the parent compound. Flow cytometric analysis of leukocytes demonstrated binding of the modified heparin to granulocytes, monocytes, and lymphocytes, the half-live being twice as long as the antifactor Xa activity. F-labeled heparin was displaced by unlabeled heparin from all three populations of leukocytes. Binding of heparin to leukocytes may play an important role in inflammation and atherosclerosis.

Pharmacodynamic study of low molecular weight dermatan sulphate (Desmin) after a single subcutaneous administration in patients with renal insufficiency.

The pharmacodynamic pattern of low molecular weight dermatan sulphate (CAS 24967-94-0, Desmin-LMWDS) was studied in patients presenting chronic renal insufficiency. Three groups of six patients were defined according to their creatinine clearance: group 1, more than 50 ml/min, group 2 between 10 and 50 ml/min and group 3 lower than 10 ml/min (haemodialized patients). Desmin-LMWDS concentrations were determined with the Heptest assay and the chromogenic specific heparin cofactor II dependent anti IIa assay. In patients of group 1 affected by moderate renal insufficiency, the pharmacodynamic profiles were roughly comparable to those obtained in normal subjects. In the two other groups, the profiles were markedly modified by the renal insufficiency. The maximal concentrations were doubled and the areas under the time-activity curve were 4-fold higher in haemodialyzed (group 3) and severe renal insufficient patients (group 2) than in patients of group 1. The clearance of the anti IIa activity were 13.98 +/- 6.25 l/h; 4.12 +/- 2.64 l/h and 2.94 +/- 1.53 l/h and the half-lives were 2.79 +/- 2.60 h, 6.15 +/- 4.02 h and 11.51 +/- 6.54 h in groups 1 to 3, respectively (p < 0.05). The Desmin-LMWDS clearance was directly correlated to the creatinine clearance (r = 0.8244, n = 18, p < 0.001). Thus, as for low molecular weight heparin, renal function plays a major role in the elimination of low molecular weight dermatan sulphate.

Biomimetic transport and rational drug delivery.

Medicine and pharmaceutics are encountering critical needs and opportunities for transvascular drug delivery that improves site targeting and tissue permeation by mimicking natural tissue addressing and transport mechanisms. This is driven by the accelerated development of genomic agents requiring targeted controlled release. Although rationally designed for in vitro activity, such agents are not highly effective in vivo, due to opsonization and degradation by plasma constituents, and failure to transport across the local vascular endothelium and tissue matrix. A growing knowledge of the addresses of the body can be applied to engineer "Bio-Logically" staged delivery systems with sequential bioaddressins complementary to the discontinuous compartments encountered--termed discontinuum pharmaceutics. Effective tissue targeting is accomplished by leukocytes, bacteria, and viruses. We are increasingly able to mimic their bioaddressins by genomic means. Approaches described in this commentary include: (a) endothelial-directed adhesion mediated by oligosaccharides and carbohydrates (e.g. dermatan sulfate as a mimic of sulfated CD44) and peptidomimetics interacting with adhesins, selectins, integrins, hyaluronans, and locally induced growth factors (e.g. vascular endothelial growth factor, VEGF) and coagulation factors (e.g. factor VIII antigen); (b) improved tissue permeation conferred by hydrophilically "cloaked" carrier systems; (c) "uncloaking" by matrix dilution or selective triggering near the target cells; and (d) target binding-internalization by terminally exposed hydrophobic moieties, cationic polymers, and receptor-binding lectins, peptides, or carbohydrates. This commentary also describes intermediate technology solutions (e.g. "hybrid drugs"), and highlights the high-resolution, dynamic magnetic resonance imaging and radiopharmaceutical imaging technologies plus the groups and organizations capable of accelerating these important initiatives.

Danaparoid sodium.

Danaparoid sodium (Orgaran, Organon) is a heparinoid glycosamino-glycuronan antithrombotic agent approved for the prophylaxis of post-operative deep vein thrombosis (DVT), which may lead to pulmonary embolism (PE) in patients undergoing elective hip replacement surgery. Danaparoid is a low molecular weight heparinoid consisting of a mixture of heparan sulphate (84%), dermatan sulphate (12%) and small amounts of chondroitin sulphate (4%), whose antithrombotic activity has been well established. Its pharmacological effect is exerted primarily by inhibiting Factors Xa (FXa) and IIa (FIIa) at a ratio greater than heparin, with a minimal effect on platelet function. Danaparoid exhibits low cross-reactivity with heparin-induced antibodies when compared with heparin or low molecular weight heparins (LMWH), thereby making it an excellent choice for the management of heparin-induced thrombocytopenia (HIT). It has excellent bioavailability following s.c. injection. Danaparoid has little effect on routine coagulation tests (activated partial thromboplastin time [aPTT], prothrombin time [PT], and thrombin time [TT]). Patients with elevated serum creatinine should be monitored carefully. For its FDA approved indication (DVT prophylaxis during hip replacement surgery), its cost per day is approximately eight times more than LMWH. Even though monitoring is not routinely necessary according to the manufacturer for its approved indication, monitoring is frequently necessary when it is used in other clinical scenarios. Its higher cost than comparable therapies for DVT prophylaxis and the low availability of the FXa assay in most non-tertiary care hospitals has limited the widespread use of danaparoid. Danaparoid has been found to be effective in the treatment of HIT although this is an off label use, despite being the most frequent reason why danaparoid is used.

A chronopharmacodynamic study on standard heparin, a low molecular weight heparin (nadroparin) and danaproid: establishing and comparing the daily variations of these drugs in rats.

The effects of dosing time on the anticoagulant activity of unfractionated heparin, low molecular weight heparin (nadroparin) and danaproid were investigated. The chronopharmacological comparisons of the drugs were done on the anti-Xa, anti-IIa activities and activated partial thromboplastin time assays. Several dosing times were considered and an analysis based on a population approach was adopted. Under unfractionated heparin, the pharmacological activities did not exhibit significant daily variations. In contrast, significant daily profiles were observed in all the biological assays performed with low molecular weight heparin. Anti-Xa and anti-IIa activities showed some fluctuations over a 24-hour period with a peak at noon. As for the variations of the activated partial thromboplastin time, two peaks were noted early in the morning and at the beginning of nightfall. As for danaproid, only a daytime maximum of anti-Xa activity could be found.

Heparin induced thrombocytopenia: diagnosis and contemporary antithrombin management.

Heparin-induced thrombocytopenia (HIT) may be complicated by severe thrombotic complications and death. Currently no specific laboratory test is available to make the diagnosis. When HIT is clinically suspected, heparin should be discontinued immediately. While no specific therapy for HIT exists, there is increasing evidence that acute antithrombin therapy may significantly reduce morbidity and mortality. Among several agents, the direct antithrombins, such as r-hirudin and argatroban, look the most promising for acute treatment.

Pharmacokinetics of danaparoid sodium, dalteparin sodium and heparin determined by inhibitory effect on the activated coagulation factor X activity after single intravenous administration in rabbits.

The inhibitory effect on the activated coagulation factor X activity (anti-Xa activity) in plasma and urine of danaparoid sodium (DAS, CAS 9005-49-6) was compared with that of dalteparin sodium (DLS, CAS 9041-08-1) and heparin (CAS 9005-49-6) after single intravenous administration at a dose of 640 anti-Xa U/kg to male rabbits. The elimination of half-life of DAS was 9.90 h and was 6.0 times longer than that of DLS and 16.5 times longer than that of heparin. The area under the plasma concentration-time curve (AUC) of DAS was 47.13 +/- 14.55 anti-Xa U.h/ml and was 2.4 times larger than that of DLS and 2.9 times larger than that of heparin. The urinary cumulative excretion of anti-Xa activity of DAS and DLS was 42.6 +/- 6.4% and 16.4 +/- 0.8% of dose, respectively, in 24 h after dosing, respectively. But the anti-Xa activity in urine was not detected at any sampling points after administration of heparin. DAS has a longer elimination half-life and a higher renal excretion of anti-Xa activity than that of DLS and heparin. Therefore, in comparison to DLS and heparin, it seems that the anticoagulant activity of DAS has a long duration.

Pharmacological actions of sulodexide.

This report summarizes the results of some of the studies that have evaluated the pharmacokinetic, pharmacodynamic, anticoagulant, and antithrombotic properties of Sulodexide, which consists of a mixture of electrophoretically fast moving heparin (80% of the mass) and dermatan sulfate (the balance), with an average product (Mr) <8000. The low molecular weight (Mr) of the constituents of Sulodexide would predict that the product has the high bioavailability associated with low-Mr heparin and low-Mr dermatan sulfate. Given orally, subcutaneously, or by intravenous injection, Sulodexide exhibits antithrombotic and profibrinolytic properties in several animal models of venous and arterial thrombosis and has relatively high affinity for endothelial (and possibly other) cells. Additionally, in a large multicenter clinical trial involving 3986 patients who had recovered from acute myocardial infarction, oral Sulodexide was associated with a 32% reduction in death and a significant reduction of left ventricular thrombus formation. Compared with heparin, low-Mr heparin, and unfractionated and low-Mr dermatan sulfates, the doses of Sulodexide required for antithrombotic efficacy suggest that the combination of heparin and dermatan sulfate in Sulodexide provides a more effective antithrombotic mechanism than heparin/low-Mr heparins (which catalyze the antiprotease actions of antithrombin III) or dermatan sulfate/low-Mr dermatan sulfate (which catalyze thrombin inhibition by heparin cofactor II).

Bioavailability of Desmin, a low molecular weight dermatan sulfate, after subcutaneous administration to healthy volunteers.

The bioavailability of two different s.c. doses of Desmin (a new low molecular weight dermatan sulfate) was evaluated in 12 healthy volunteers (6 men, 6 women aged 22-45 years) who were injected, on 3 separate days and with a wash-out period of at least 21 days between each administration, with 200 and 300 mg of Desmin by the s.c. route and 200 mg by the i.v. route. Immediately before injection and at various times thereafter (after 15 min and 30 min for i.v. only and after 1, 2, 3, 4, 6, 8, 12, and 24 h for both s.c. and i.v. dosing), blood samples were drawn to investigate bioavailability by measuring several coagulation parameters: activated partial thromboplastin time, thrombin time, inhibition of factor Xa, Heptest, and heparin cofactor II. Furthermore the local tolerance of the s.c. and i.v. injections were investigated. The s.c. administration of the two Desmin doses had a negligible effect on the activated partial thromboplastin time and a very small effect on the thrombin time, measured with human thrombin; in contrast, Heptest, heparin cofactor II, and anti-Xa activities increased, with a good drug bioavailability (more than 100%). The plasma effects of Desmin were dose dependent only when measured by Heptest, which also gave a greater response after the s.c. administrations. There were no symptoms of intolerance or pain at the injection site after single i.v. and s.c. Desmin administration.

Danaparoid. A review of its pharmacology and clinical use in the management of heparin-induced thrombocytopenia.

Danaparoid, a low molecular weight heparinoid consisting of a mixture of heparan, dermatan and chondroitin sulfates, has well established antithrombotic activity. The drug has a high antifactor Xa to antifactor IIa (thrombin) activity ratio, a low tendency to cause bleeding and minimal effects on the fibrinolytic system. Danaparoid has a low cross-reactivity rate with heparin-associated antiplatelet antibodies (0 to 20%; mean approximately 10%). This represents a significant advantage over low molecular weight heparins (LMWHs) as a potential replacement agent for unfractionated heparin (UFH) in patients with immune-mediated (type II) heparin-induced thrombocytopenia (HIT). In a worldwide compassionate-use programme involving a total of 667 patients with HIT to date, 93% of danaparoid treatment courses were considered to be successful. Thrombocytopenia resolved in 91% of episodes. In a multicentre randomised comparative trial of danaparoid and dextran in patients with HIT plus thrombosis (HITT), significantly more danaparoid than dextran recipients had resolution of thromboses, and an effective clinical response was achieved in significantly more danaparoid recipients. Results of a retrospective case-controlled study of danaparoid and ancrod in patients with HITT showed significantly fewer new or progressive thromboses with danaparoid. In the compassionate-use programme, danaparoid was associated with a mortality rate of 10.4% during treatment (up to 3.5 years) and 7.8% during the follow-up period (3 months). 14 of 114 deaths during the follow-up period were considered to be related to danaparoid therapy. A mortality rate of 23.5% was reported in patients accepted for but not treated with, danaparoid. Mortality rates with danaparoid, ancrod and dextran in the comparative studies were similar (7, 11 and 12%, respectively). Severe bleeding was reported in 3.1% of patients in the compassionate-use programme, persistent or recurrent thrombocytopenia in 2.6% and new thromboembolic events/extension of existing thrombosis in 1.7%. The incidence of bleeding was similar with danaparoid and dextran in a comparative trial. Although in vitro cross-reactivity does not always translate into clinical cross-reactivity, testing is currently recommended, when possible, before initiation of danaparoid therapy. Thus, danaparoid appears to be an effective and well tolerated replacement agent for UFH in many patients with HIT who require further anticoagulation. The drug has low cross-reactivity with HIT-associated antibodies. Further comparative trials are needed to confirm these promising findings.

Simultaneous determination of dermatan sulfate and oversulfated dermatan sulfate in plasma by high-performance liquid chromatography with postcolumn fluorescence derivatization.

A chemical method for the determination of dermatan sulfate (DS) and oversulfated dermatan sulfate has been developed and applied to the pharmacokinetic study of these polysaccharides in experimental animals. The analytical procedure includes a simple preparation step of administered DS and oversulfated DS from blood plasma, HPLC for the separation and detection of DS and oversulfated DS using an Asahipak NH2P-50 column, fluorometric reaction of the polysaccharides with guanidine in a strong alkaline medium. DS and oversulfated DS were extracted from plasma by treating it with proteinase to remove plasma proteins and recovered with endogenous plasma glycosaminoglycans by ethanol precipitation. Finally, DS and oversulfated DS were analyzed by fluorometric HPLC. The detection limits of DS and oversulfated DS were 10 and 20 ng, respectively. Furthermore, we demonstrated that artificial oversulfation of DS increased its biological half-life after intravenous administration to rats.

Effects of low-molecular-weight dermatan sulfate on coagulation, fibrinolysis and tissue factor pathway inhibitor in healthy volunteers.

Low-molecular-weight (LMW)-dermatan sulfate (Desmin) with the mean molecular weight of 5600 Da has been obtained by limited depolymerization of natural dermatan sulfate. The pharmacokinetic and pharmacodynamic data of 100 and 200 mg were analyzed after intravenous injection and of 50, 100 and 200 mg after subcutaneous injection on tissue factor pathway inhibitor (TFPI) antigen and activity, heparin cofactor (HC) II activity, HeptestTM coagulation value, chromogenic S-2222 anti-factor Xa (aXa) assay, activated partial thromboplastin time (APTT), thrombin clotting time (TCT), plasminogen, tissue plasminogen activator activity (t-PA) and plasminogen activator inhibitor (PAI). After i.v.injection of 100 mg and 200 mg Desmin TFPI antigen and activity increased 2.2- and 2.7-fold, and returned to normal values within 60 and 90 min, respectively. Using the HC II assay the elimination half-lives (T1/2 el) increased from 1.9 h to 3.3 h with increasing doses of LMW-dermatan sulfate. T1/2 el were 4.3 and 6.9 h with the Heptest assay and 3.3 and 5.1 with the aXa method, respectively. APTT, TCT and the fibrinolytic parameters were not modified by either dose of i.v. LMW-dermatan sulfate. After s.c. administration of 100 mg or 200 mg LMW-dermatan sulfate no increase of TFPI antigen or activity was detected. T1/2 el was 5.6 h using HC II method, 11.1 h using Heptest and 7.8 h with the aXa activity. The total clearance was about ten-fold higher when determined by the HC II method compared with Heptest and aXa method. The volume of distribution (VD) increased with increasing doses of s.c. LMW-dermatan sulfate and was highest with the HC II method. Intravenous administration of 100 mg protamine chloride 15 min after i.v. dosing of 100 mg LMW-dermatan sulfate did not modify TFPI, coagulation or fibrinolytic parameters. Further analysis of the complex mechanism of action has to include studies which should explain the low release of TFPI in relation to the antithrombotic effects of LMW-dermatan sulfate.

Pharmacodynamic characteristics of low-molecular-weight dermatan sulphate after subcutaneous administration in acute myocardial infarction.

Sixteen patients (5 female and 11 male, mean age 59.1 years) who had had an acute myocardial infarction within the previous 7 days, were enrolled in an open pharmacodynamic study. Patients were randomly allocated to two treatment groups and given a single subcutaneous dose of 100 or 200 mg of a new low-molecular-weight dermatan sulphate. The drug pharmacodynamic profile was determined 1, 2, 4, 6, 8, 12 and 24 h after administration. The following coagulation and fibrinolysis tests were performed: activated partial thromboplastin time, thrombin time, activated factor X inhibition, Heptest (global clotting time), heparin cofactor II affinity, functional and antigenic plasminogen activator inhibitor and fibrin plate assay. Both Heptest and heparin cofactor II affinity were significantly increased (P < 0.001) in a dose-dependent manner. The XaI was enhanced, though to a lesser extent. None of the other coagulation or fibrinolysis tests showed significant changes at either dose. Systemic and local tolerance were always very good.

Intramuscular dermatan sulfate MF701 in patients with hip fracture: relationship between pharmacokinetics and antithrombotic efficacy.

Two groups of 23 and 84 patients with hip fracture received intramuscularly 100 and 300 mg dermatan sulfate (MF701) b.i.d., respectively, for the prophylaxis of deep vein thrombosis. Median duration of treatment was 17 and 16 days, respectively. Four blood samples were collected from each patient while under treatment. Plasma levels of dermatan sulfate were determined by a chromogenic substrate assay. A one-compartment model for multiple doses was employed to estimate the pharmacokinetic parameters. Fitting was applied to mean plasma concentrations calculated for each sampling time and weighted according to the number of samples available at each time. Thrombin clotting time was measured on the same plasma samples. Antithrombotic efficacy was assessed by bilateral venography. Plasma levels of dermatan sulfate increased gradually throughout the treatment, indicating a marked accumulation process. Time to reach steady-state was 14 or 9 days with 100 or 300 mg b.i.d., respectively. This was due to an apparent prolonged terminal half-life (68 or 43 h), which actually reflected slow absorption from the injection sites. The clinical efficacy of MF701 in preventing DVT was found to be dependent on the plasma concentration of the drug and also, but less significantly, on the prolongation of thrombin clotting time. Dermatan sulfate plasma levels greater than 9 micrograms/ml are advisable to optimize efficacy in hip fracture patients.