l-Arginine is the principal physiological precursor of nitric oxide (NO, a key neurotransmitter) that plays a versatile role in the physiology of the gastrointestinal tract. In this study, the efficacy of l-arginine in enhancing intestinal absorption of ardeparin, a low-molecular-weight heparin (LMWH) was investigated in Caco-2 cell monolayers and a rat model. Regional permeability studies using rat intestine were performed using a modified Ussing chamber. Cell viability in the presence of various concentrations of enhancer was determined by MTT assay. Furthermore, the eventual mucosal epithelial damage was histologically evaluated. LMWH formulated with l-arginine was administered orally to mate Sprague-Dawley rats and the absorption of LMWH was determined by measuring plasma anti-factor Xa activity. Higher ardeparin in-vitro permeability (~3 fold) compared with control was observed in the presence of 2% l-arginine. Regional permeability studies indicated predominant absorption in the colon region. Cell viability studies showed no significant cytotoxicity below 0.8% l-arginine. The oral bioavailability of ardeparin formulated with l-arginine (250 mg kg−1) was increased by ~2 fold compared with control. The formulation was well tolerated by the rats and no abnormal histopathological findings were observed in intestinal tissues of rats exposed to l-arginine. These results suggest that l-arginine may be useful in enhancing the intestinal absorption of LMWHs.
The primary objective of this study was to evaluate sodium caprate as an
oral penetration enhancer for low molecular weight heparin (LMWH), ardeparin.
In vitro studies using Caco-2 cell monolayer indicated that
0.0625% of sodium caprate gave approximately 2-fold enhancement of
ardeparin compared to negative control with almost 100% cell
survival as evaluated by MTT cytotoxicity assay. In vivo
studies in rats with ardeparin (1200 IU/kg) and sodium caprate (100 mg/kg) led
to a relative bioavailability of 27% with plasma anti-factor Xa
levels within the therapeutic range (> 0.2 IU/ml). Moreover, under these
conditions, histological examination provided evidence that there was no damage
to the gastrointestinal wall. Regional permeability studies using rat intestine
indicated the colon as the region of maximum permeation. These results suggest
that, at the dose administered, sodium caprate acts as a relatively safe and
efficient absorption enhancer in the quest for alternatives for the oral
delivery of LMWH.
Sodium caprate; low molecular weight heparin; Caco-2 cell monolayer; absorption enhancer; ardeparin; oral absorption
Zonula occludens toxin (Zot) is an enterotoxin obtained from the
bacterium vibrio cholerae that has been shown to reversibly and
safely open the tight junctions and enhance paracellular transport. AT1002 is a
novel synthetic hexapeptide derived from Zot. The hypothesis to be tested in
this study is that AT1002 enhances the oral absorption of ardeparin, a low
molecular weight heparin (LMWH). To test this hypothesis, drug transport through
Caco-2 cell monolayers was monitored in the presence and absence of AT1002.
Regional permeability studies using rat intestine were performed. Cell viability
in the presence of various concentrations of enhancer was determined. The
absorption of ardeparin after oral administration in rats was measured by
anti-factor Xa assay. Furthermore, the eventual mucosal and epithelial damage
was histologically evaluated. Higher ardeparin permeability (~2-fold) compared
to control was observed in the presence of 0.025% of AT1002.
Regional permeability studies revealed that the permeability of ardeparin across
the duodenal membrane was improved by the AT1002. Cell viability studies showed
no significant cytotoxicity below 0.0028% of AT1002. In the presence
of 100 μg/kg of AT1002, ardeparin oral bioavailability was
significantly increased (Frelative/s.c ~
20.5%). Furthermore, AT1002 at a dose of 100 μg/kg did
not induce any observable morphological damage on gastrointestinal (GI) tissues
in vivo. These in vivo and in
vitro results suggest that the co-administration of LMWH with
AT1002 may be a useful delivery strategy to increase its permeability and hence
AT1002; low molecular weight heparin; enhancer; oral delivery; zonula occludens toxin
This study tests the hypothesis that positively charged polyethylenimines (PEIs) enhance nasal absorption of low molecular weight heparin (LMWH) by reducing the negative surface charge of the drug molecule. Physical interactions between PEIs and LMWH were studied by Fourier transform infrared (FTIR) spectroscopy, particle size analysis, conductivity measurements, zeta potential analysis, and azure A assay. The efficacy of PEIs in enhancing nasal absorption of LMWH was studied by administering LMWH formulated with PEI into the nose of anesthetized rats and monitoring drug absorption by measuring plasma anti-factor Xa activity. The metabolic stability of LMWH was evaluated by incubating the drug in rat nasal mucosal homogenates. FTIR spectra of the LMWH-PEI formulation showed a shift in peak position compared to LMWH or PEI alone. Decreases in conductivity, zeta potential and the amount of free LMWH in the PEI-LMWH formulation, as revealed by azure A assay, suggest that PEIs possibly neutralize the negative surface charge of LMWH. The efficacy of PEI in enhancing the bioavailability of nasally administered LMWH can be ranked as PEI-1000 KDa ≥ PEI-750 KDa > PEI-25 KDa. When PEI-1000 KDa was used at a concentration of 0.25%, there was a 4-fold increase in both the absolute and relative bioavailabilities of LMWH compared to the control formulation. Overall, these results indicate that polyethylenimines can be used as potential carriers for nasally administered LMWHs.
low molecular weight heparin; polyethylenimine; nasal absorption; enoxaparin; conductivity
The development of a non-invasive drug delivery system for unfractionated heparin (UFH) and low molecular weight heparins (LMWHs) has been the elusive goal of several research groups since the initial discovery of this glycosaminogylcan by McLean in 1916. After a brief update on current parenteral formulations of UFH and LMWHs, this review revisits past and current strategies intended to identify alternative routes of administration (e.g. oral, sublingual, rectal, nasal, pulmonary and transdermal). The following strategies have been used to improve the bioavailability of this bioactive macromolecule by various routes: (i) enhancement in cell-membrane permeabilization, (ii) modification of the tight-junctions, (iii) increase in lipophilicity and (iv) protection against acidic pH of the stomach. Regardless of the route of administration, a simplified unifying principle for successful non-invasive macromolecular drug delivery may be: “to reversibly overcome the biological, biophysical and biochemical barriers and to safely and efficiently improve the in vivo spatial and temporal control of the drug in order to achieve a clinically acceptable therapeutic advantage”. Future macromolecular drug delivery research should embrace a more systemic approach taking into account recent advances in genomics/proteomics and nanotechnology.
Alternative routes; Bioactive macromolecule; Drug delivery; Non-invasive; Heparin
Traditionally, acute deep venous thrombosis (DVT) is treated with intravenous heparin followed by oral anticoagulants. With the advent of the low-molecular-weight heparins (LMWHs), this strategy is changing dramatically. LMWHs are compounds derived from standard unfractionated heparin that offer distinct clinical advantages over unfractionated heparin, including better bioavailability, longer half-life, and a more predictable anticoagulant response that obviates the need for laboratory monitoring. The common side effects of unfractionated heparin, including bleeding, thrombocytopenia, and osteoporosis, may be less common with LMWH. For the treatment of established venous thromboembolism, LMWH is at least as safe and effective as unfractionated heparin. Recent studies demonstrate that home therapy of DVT with LMWH, compared with inpatient therapy with unfractionated heparin, produces comparable clinical outcomes and patient satisfaction, with dramatic cost savings. With careful patient selection, home therapy of venous thromboembolism is quickly becoming the new standard of care.
Over the last 15 years, low-molecular-weight heparins (LMWHs) have been accepted as the “gold standard” for pharmaceutical thromboprophylaxis in patients at high risk of venous thromboembolism (VTE) in most countries around the world. Patients undergoing major orthopedic surgery (MOS) represent a population with high risk of VTE, which may remain asymptomatic or become symptomatic as deep vein thrombosis or pulmonary embolism. Numerous trials have investigated LMWH thromboprophylaxis in this population and demonstrated high efficacy and safety of these substances. However, LMWHs have a number of disadvantages, which limit the acceptance of patients and physicians, especially in prolonged prophylaxis up to 35 days after MOS. Consequently, new oral anticoagulants (NOACs) were developed that are of synthetic origin and act as direct and very specific inhibitors of different factors in the coagulation cascade. The most developed NOACs are dabigatran, rivaroxaban, and apixaban, all of which are approved for thromboprophylaxis in MOS in a number of countries around the world. This review is focused on the pharmacological characteristics of apixaban in comparison with other NOACs, on the impact of NOAC on VTE prophylaxis in daily care, and on the management of specific situations such as bleeding complications during NOAC therapy.
major orthopedic surgery; apixaban; dabigatran; edoxaban; rivaroxaban; deep vein thrombosis; venous thromboembolism; VTE prophylaxis
Norrby K, Nordenhem A. Dalteparin, a low-molecular-weight heparin, promotes angiogenesis mediated by heparin-binding VEGF-A in vivo. APMIS 2010; 118: 949–57.
Tumors are angiogenesis dependent and vascular endothelial growth factor-A (VEGF-A), a heparin-binding protein, is a key angiogenic factor. As chemotherapy and co-treatment with anticoagulant low-molecular-weight heparin (LMWH) are common in cancer patients, we investigated whether angiogenesis in vivo mediated by VEGF-A is modulated by metronomic-type treatment with: (i) the LMWH dalteparin; (ii) low-dosage cytostatic epirubicin; or (iii) a combination of these two drugs. Using the quantitative rat mesentery angiogenesis assay, in which angiogenesis was induced by intraperitoneal injection of very low doses of VEGF, dalteparin sodium (Fragmin®) and epirubicin (Farmorubicin®) were administered separately or in combination by continuous subcutaneous infusion at a constant rate for 14 consecutive days. Dalteparin was administered at 27, 80, or 240 IU/kg/day, i.e., doses that reflect the clinical usage of this drug, while epirubicin was given at the well-tolerated dosage of 0.4 mg/kg/day. While dalteparin significantly stimulated angiogenesis in an inversely dose-dependent manner, epirubicin did not significantly affect angiogenesis. However, concurrent treatment with dalteparin and epirubicin significantly inhibited angiogenesis. The effect of dalteparin is the first demonstration of a proangiogenic effect of any LMWH in vivo. The fact that co-treatment with dalteparin and epirubicin significantly inhibited angiogenesis suggests a complex drug effect.
Angiogenesis; low-molecular-weight heparin; dalteparin; epirubicin; VEGF-A; metronomic chemotherapy
Patients undergoing anticoagulation with heparin or low molecular weight heparin (LMWH) require a superior antidote that possesses more selective biological actions and a better safety profile than protamine. We had previously developed 2 low molecular weight protamine (LMWP) fractions (TDSP4 and TDSP5) from thermolysin-digested protamine as potential nontoxie, heparin-neutralizing agents. In this, the second article in this series, studies focused on in vitro evaluation of heparin/LMWH-neutralizing efficacy and putative toxicity. These LMWP fractions, particularly TDSP5, were effective and fully capable of neutralizing a broad spectrum of heparin-induced anticoagulant activities (ie, aPTT, anti-Xa, and anti-IIa activities). Additionally, these LMWP fractions could neutralize the activities of commercial LMWH. As assessed by the anti-Xa assay, TDSP5 was as effective as, although less potent than, protamine in reversing the activity of Mono-Embolex (molecular weight 5000–7000) and 2 other different sizes (molecular weight of 3000 and 5000 d) of LMWH preparations. Furthermore, compared with protamine, TDSP5 exhibited a much-reduced toxicity and thus an improved safety profile, as reflected by its reduced ability to activate the complement system and cross-react with the antiprotamine antibodies, which are 2 primary indices of protamine toxicity.
Heparin/LMWH neutralization; protamine toxicity; aPTT clotting assay; anti-Xa assay; complement Activation; immunogenicity; cross-reactivity
Elderly people represent a patient population at high thromboembolic risk, but also at high hemorrhagic risk. There is a general tendency among physicians to underuse anticoagulants in the elderly, probably both because of underestimation of thromboembolic risk and overestimation of bleeding risk. The main indications for anticoagulation are venous thromboembolism (VTE) prophylaxis in medical and surgical settings, VTE treatment, atrial fibrillation (AF) and valvular heart disease. Available anticoagulants for VTE prophylaxis and initial treatment of VTE are low molecular weight heparins (LMWH), unfractionated heparin (UFH) or synthetic anti-factor Xa pentasaccharide fondaparinux. For long-term anticoagulation vitamin K antagonists (VKA) are the first choice and only available oral anticoagulants nowadays. Assessing the benefit-risk ratio of anticoagulation is one of the most challenging issues in the individual elderly patient, patients at highest hemorrhagic risk often being those who would have the greatest benefit from anticoagulants. Some specific considerations are of utmost importance when using anticoagulants in the elderly to maximize safety of these treatments, including decreased renal function, co-morbidities and risk of falls, altered pharmacodynamics of anticoagulants especially VKAs, association with antiplatelet agents, patient education. Newer anticoagulants that are currently under study could simplify the management and increase the safety of anticoagulation in the future.
anticoagulation; elderly patients; venous thromboembolism; hemorrhagic risk; atrial fibrillation; thrombin inhibitors; factor Xa inhibitor
Currently low molecular weight heparin (LMWH) is administered as subcutaneous injection. This study sought to investigate the feasibility of LMWH as an inhalable dry powder (DPI) formulation and evaluate the interaction of the drug with lactose when used as a carrier. The study also compares the extent of pulmonary absorption of LMWH administered as a dry powder with that administered as an aerosolized aqueous solution.
The formulations were prepared by mixing LMWH in an aqueous solution of lactose followed by lyophilization of the resulting solution. The lyophilized preparation was then ground and sieved. Physical characterization of the formulations was performed by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), particle size analysis, and determination of aerodynamic diameter. For in vivo studies, formulations were administered to anesthetized rats, and drug absorption was monitored by measuring plasma antifactor Xa activity.
Results and Conclusions
In the FTIR scan, all characteristic peaks of lactose and LMWH were observed, suggesting that there was no strong interaction between lactose and LMWH. Although the aerodynamic diameter of the formulation (DPI-2) that was sieved through 170- and 230-mesh screens was similar to that of the formulation (DPI-1) sieved through 120- and 170-mesh screens, the particle sizes of the two formulations were significantly different. Dry powder formulations of LMWH were better absorbed compared to an inhalable solution of LMWH. One of the dry powder formulations (DPI-2) produced an almost 1.5-fold increase in the relative bioavailability (41.6%) compared to the liquid formulation of LMWH (32.5%). Overall, the data presented here suggest that lactose does not adversely affect the physical-chemical characteristics of the drug, and that lactose can be used as a carrier for pulmonary delivery of LMWH.
LMWH; inhalation; dry powder; pulmonary absorption
A 56-yr-old man with lung adenocarcinoma presented with subsegmental pulmonary thrombosis. Platelet count on presentation was 531×109/L. The patient was anticoagulated with subcutaneous low molecular weight heparin (LMWH). Next day, oral anticoagulation was initiated with 5 mg of warfarin once daily with LMWH and LMWH was discontinued at third hospital day. On the third day of oral anticoagulation therapy, he complained of left leg swelling and prolonged painful penile erection of 24 hr-duration. His platelet count reached a nadir 164×109/L at that time, and the patient had a deficiency of protein C and S, with an activity level of 16% and 20% of normal value. Warfarin was stopped and he underwent penile aspiration. The next day, left leg edema and penile erection was disappeared, but penile and glans penis necrosis was started. This case illustrates that processes underlying heparin-induced thrombocytopenia (HIT) may also underlie warfarin-induced skin necrosis.
Penis; Necrosis; Warfarin; Heparin
The authors present a case of a 27-year-old multiparous woman, with multiple thrombophilia, whose pregnancy was complicated with deep venous thrombosis requiring placement of a vena cava filter. At 15th week of gestation, following an acute deep venous thrombosis of the right inferior limb, anticoagulant therapy with low-molecular-weight heparin (LMWH) was instituted without improvement in her clinical status. Subsequently, at 18 weeks of pregnancy, LMWH was switched to warfarin. At 30th week of gestation, the maintenance of high thrombotic risk was the premise for placement of an inferior vena cava filter for prophylaxis of pulmonary embolism during childbirth and postpartum. There were no complications and a vaginal delivery was accomplished at 37 weeks of gestation. Venal placement of inferior vena cava filters is an attractive option as prophylaxis for pulmonary embolism during pregnancy.
Commercial low molecular weight heparins (LMWHs) are prepared by several methods including peroxidative cleavage, nitrous acid cleavage, chemical ß-elimination, and enzymatic β-elimination. The disadvantages of these methods are that strong reaction conditions or harsh chemicals are used and these can result in decomposition or modification of saccharide units within the polysaccharide backbone. These side-reactions reduce product quality and yield. Here we show the partial photolysis of unfractionated heparin can be performed in distillated water using titanium dioxide (TiO2). TiO2 is a catalyst that can be easily removed by centrifugation or filtration after the photochemical reaction takes place, resulting in highly pure products. The anticoagulant activity of photodegraded LMWH (pLMWH) is comparable to the most common commercially available LMWHs (i.e., Enoxaparin and Dalteparin). 1H NMR spectra obtained show that pLMWH maintains the same core structure as unfractionated heparin. This photochemical reaction was investigated using liquid chromatography/mass spectrometry (LC/MS) and unlike other processes commonly used to prepare LMWHs, photochemically preparation affords polysaccharide chains of reduced length having both odd and even of saccharide residues.
Low molecular weight heparin; Photochemical depolymerization; Titanium dioxide; NMR; LC-MS
The peak incidence of venous thrombo-embolism (VTE) occurs 3 weeks following hip arthroplasty surgery and current guidelines proposing VTE prophylaxis continuing for 4 weeks after surgery. This study first compares the duration of treatment and satisfaction between patients prescribed low molecular weight heparin (LMWH) and rivaroxaban, a new oral Factor Xa inhibitor, following elective hip arthroplasty; and second, surveys the duration of LMWH use in other units.
SUBJECTS AND METHODS
An international survey detailing the use of LMWH was performed. A prospective audit was performed of 100 hip replacements, with 50 prescribed 40 mg once daily of subcutaneous enoxaparin and subsequently 50 patients prescribed 10 mg once daily of oral rivaroxaban. The duration of treatment, patient satisfaction and complications for both cohorts was quantified and compared against published evidence-based guidelines.
The survey demonstrated that four out of 39 (10.2%) units that routinely prescribe LMWH do so for at least 4 weeks following surgery. The audit demonstrated that rivaroxaban afforded a superior mean duration of postoperative VTE prophylaxis (35 days vs 5.4 days; P < 0.05) and superior patient satisfaction. There was no difference in the incidence of bleeding, wound infection or thrombotic complications.
This study demonstrates that patients are exposed to an increased VTE risk following hip replacement surgery due to the inadequate prescription of LMWH. This is poor clinical practice, contrary to current evidence-based guidelines and has potential medicolegal implications. The prescription of rivaroxaban affords a superior patient compliance compared with subcutaneous LMWH, thus ensuring that patients receive VTE prophylaxis for the current recommend period of time.
Rivaroxaban; Low molecular weight heparin; Thromboprophylaxis
This study was performed to test the feasibility of chitosan and polylactic-co-glycolic acid (PLGA) incorporated nanoparticles as sustained-release carriers for the delivery of negatively charged low molecular weight heparin (LMWH). Fourier transform infrared (FTIR) spectrometry was used to evaluate the interactions between chitosan and LMWH. The shifts, intensity, and broadening of the characteristic peaks for the functional groups in the FTIR spectra indicated that strong interactions occur between the positively charged chitosans and the negatively charged LMWHs. Three types of LMWH nanoparticles (NP-1, NP-2, and NP-3) were prepared using chitosan with or without PLGA: NP-1 nanoparticles were formed by polyelectrolyte complexation after single mixing, NP-2 nanoparticles were prepared by polyelectrolyte complexation after single emulsion–diffusion–evaporation, and NP-3 nanoparticles were optimized by double emulsion–diffusion–evaporation. NP-3 nanoparticles of LMWH prepared by the emulsion–diffusion–evaporation method showed significant differences in particle morphology, size, zeta potential, and drug release profile compared to NP-1 nanoparticles formed by polyelectrolyte complexation. Another ionic complex of LMWH with chitosan-incorporated PLGA nanoparticles (NP-2) showed lower drug entrapment efficiency than that of NP-1 and NP-3. The drug release rate of NP-3 was slower than the release rates of NP-1 and NP-2, although particle morphology of NP-3 was similar to that of NP-2. Cell viability was not adversely affected when cells were treated with all three types of nanoparticles. The data presented in this study demonstrate that nanoparticles formulated with chitosan–PLGA could be a safe sustained-release carrier for the delivery of LMWH.
chitosan; low molecular weight heparin; nanoparticles; PLGA
Low-molecular-weight heparin (LMWH) is the drug of choice to prevent venous thrombosis in pregnancy, but the optimal dose for prevention while avoiding bleeding is unclear. This study investigated whether therapeutic doses of LMWH increase the incidence of postpartum haemorrhage (PPH) in a retrospective controlled cohort.
All pregnant women who received therapeutic doses of LMWH between 1995 and 2008 were identified in the Academic Medical Center, Amsterdam, The Netherlands. The controls were women registered for antenatal care in the same hospital who did not use LMWH during pregnancy, matched by random electronic selection for age, parity and delivery date to LMWH users. The incidence of PPH (blood loss >500 ml), severe PPH (blood loss >1000 ml) and median blood loss were compared in two cohorts of LMWH users and non-users.
The incidence of PPH was 18% in LMWH users (N=95) and 22% in non-users (N=524) (RR 0.8; 95% CI 0.5 to 1.4). The incidence of severe PPH was 6% in both groups (RR 1.2; 0.5 to 2.9). The median amount of blood loss differed only in normal vaginal deliveries. It was 200 ml in LMWH users and 300 ml in non-users (difference −100 ml; 95% CI −156 to −44).
Therapeutic doses of LMWH in pregnancy were observed not to be associated with a clinically meaningful increase in the incidence of PPH or severe PPH in women delivered in this hospital, although this observation may be confounded by the differential use of strategies to prevent bleeding. A randomised controlled trial is necessary to provide a definite answer about the optimal dose of LMWH in pregnancy.
To compare the incidence of PPH (ie, blood loss >500 ml in the first 24 h of delivery) in two cohorts of pregnant women who were treated with therapeutic doses of LMWH and those who were not.
To compare the incidence of severe PPH (blood loss >1000 ml) in two cohorts of pregnant women who were treated with therapeutic doses of LMWH and those who were not.
To compare the median blood loss in two cohorts of pregnant women who were treated with therapeutic doses of LMWH and those who were not.
Therapeutic doses of LMWH in pregnancy were not associated with a clinically meaningful increase in the incidence of PPH (RR 0.8; 95% CI 0.5 to 1.4) or severe PPH (RR 1.2; 0.5 to 2.9) in women delivered in our hospital.
The median amount of blood loss differed only in normal vaginal deliveries. It was lower in LMWH users (200 ml) than in non-users (300 ml) (difference −100 ml; 95% CI −156 to −44).
Strength and limitation of this study
This is the largest cohort of pregnancies treated with high doses of LMWH.
Although this was a controlled cohort study, it is likely that strategies to decrease the risk of PPH differed between women who were treated with LMWH and controls.
Binding interactions between low molecular weight heparin (LMWH) and heparin-binding peptides (HBP) have been applied as a strategy for the assembly of hydrogels that are capable of sequestering growth factors and delivering them in a controlled manner. In this work, the assembly of four-arm star poly(ethylene glycol) (PEG)–LMWH conjugate with PEG–HBP conjugates has been investigated. The interactions between LMWH and the heparin-binding regions of antithrombin III (ATIII) or the heparin interacting protein (HIP) have been characterized via heparin affinity chromatography and surface plasmon resonance (SPR); results indicate that the two peptides have slightly different affinities for heparin and LMWH, and bind LMWH with micromolar affinity. Solutions of the PEG–LMWH and of mixtures of the PEG–LMWH and PEG–HBP were characterized via both bulk rheology and laser tweezer microrheology. Interestingly, solutions of PEG–LMWH (2.5 wt % in PBS) form hydrogels in the absence of PEG–ATIII or PEG–HIP, with storage moduli, determined via bulk rheological measurements, in excess of the loss moduli over frequencies of 0.1–100 Hz. The addition of PEG–ATIII or PEG–HIP increases the moduli in direct proportion to the number of cross-links introduced. Characterization of the hydrogels via microrheology shows the gel microstructure is composed of polymer-rich fibrillar structures surrounded by polymer-depleted buffer. Potential applications of these hydrogels are discussed.
Low-molecular-weight heparins (LMWHs) are safe and effective anticoagulant options for cardiovascular patients when applied as body weight-adjusted doses. However, there are some barriers that make it difficult to implement weight-adjusted doses in clinical practice. Therefore, it is vital to learn the dosing practices of LMWH and its efficacy and safety in clinical practice.
A retrospective study was conducted in cardiovascular inpatients who had received at least one dose of LMWH during a 6-month period. Appropriateness of LMWH dosing was determined and major clinical outcomes (major adverse vascular events and major bleeding) during hospitalization were evaluated.
A total of 376 admissions representing 364 patients received LMWH treatment. Of these, 17.0% (64/376) of admissions did not have body weight records. Of the 312 admissions included for the outcome study, only 34 cases (10.9%) received the recommended doses of LMWH, while 51 cases (16.3%) received mild underdoses, 223 cases (71.5%) received major underdoses and 4 (1.3%) received excess doses. There were 10 major adverse vascular events, which occurred more often in patients receiving excess doses of LMWH than in patients receiving recommended, mild or major underdoses (50%, 2.9%, 2.0% and 2.7%, respectively, P < 0.001). After multivariable analysis, severe renal insufficiency was an independent risk factor for major adverse vascular events [odds ratio (OR), 31.93; 95% confidence interval (CI), 5.99-170.30; P < 0.001]. No major bleeding was recorded.
Underdose of LMWH is commonly used in cardiovascular inpatients, which was suboptimal according to guidelines. Using LMWH at a fixed, low dose for treatment purposes in patients without severe renal insufficiency was not associated with a higher risk of adverse vascular events in the current study, though larger studies with extended follow-ups are required to fully assess the long-term consequences of LMWH underdosing.
Low molecular weight heparin; Dosing practice; Cardiovascular inpatients; Efficacy; Safety
Lung cancer is one of the most highly malignant tumors, and a significant threat to human health. Lung cancer patients often exhibit tumor cell invasion and metastasis, which often render current treatments ineffective. Recently, the beneficial effects of low molecular weight heparin (LMWH) on cancer metastasis were reported in pre-clinical research studies. LMWH may be a potential drug for cancer therapy. However, the mechanism of LMWH on the invasion and metastasis of cancer has yet to be determined. This study investigated the effects of Fraxiparine on the proliferation, invasion and metastasis of the human lung adenocarcinoma A549 cell line. MTT assay and flow cytometry showed that Fraxiparine slightly inhibited the cell viability dose- and time-dependently, but did not arrest the A549 cells in the G1 phase nor induce early apoptosis. The transwell chamber assay showed that Fraxiparine significantly suppressed the invasion and migration of the A549 cells in vitro. Fraxiparine also markedly inhibited the adhesion of the A549 cells to Matrigel. The RT-PCR assay demonstrated that the reduction in invasion and metastasis may be related to the up-regulation of nm23-H1 and the down-regulation of the heparanase expression. Moreover, the RT-PCR assay and Western blot analysis demonstrated that down-regulation of the expression of integrin β1 and β3, as well as that of matrix metalloproteinase-2 and −9 may be responsible for the inhibition of the invasion and metastasis of A549 cells by Fraxiparine.
lung cancer; low molecular weight heparin; fraxiparine; invasion; metastasis
Since low-molecular-weight heparins (LMWHs) are eliminated preferentially via the kidneys, the potential for accumulation of these agents (and an increased risk of bleeding) is of particular concern in populations with a high prevalence of renal impairment, such as the elderly and patients with cancer. The risk of clinically relevant accumulation of anticoagulant activity as a result of a reduction in renal elimination appears to differ between LMWHs. This review describes the elimination pathways for LMWHs and assesses whether the relative balance between renal and non-renal (cellular) clearance may provide a mechanistic explanation for the differences in accumulation that have been observed between LMWHs in patients with impaired renal function. Clearance studies in animals, cellular binding studies and clinical studies all indicate that the balance between renal and non-renal clearance is dependent on the molecular weight (MW): the higher the MW of the LMWH, the more the balance is shifted towards non-renal clearance. Animal studies have also provided insights into the balance between renal and non-renal clearance by examining the effect of selective blocking of one of the elimination pathways, and it is most likely that cellular clearance is increased to compensate for decreased renal function. Tinzaparin (6,500 Da) has the highest average MW of the marketed LMWHs, and there is both clinical and preclinical evidence for significant non-renal elimination of tinzaparin, making it less likely that tinzaparin accumulates in patients with renal impairment compared with LMWHs with a lower MW distribution. On the basis of our findings, LMWHs that are less dependent on renal clearance may be preferred in patient populations with a high prevalence of renal insufficiency.
Tinzaparin; Low-molecular-weight heparin (LMWH); Elimination; Clearance; Renal insufficiency; Pharmacokinetics; Pharmacodynamics; Clinical; Non-clinical
Low-molecular-weight heparins (LMWH) appear to prolong survival of patients with cancer. Such a beneficial effect is thought to be associated with interruption of molecular mechanisms involving the heparan sulfate (HS) chains of cell surface and extracellular matrix proteoglycans (HSPGs), growth factors and their receptors, heparanase, and selectins. The beneficial effects of heparin species could also be associated with their ability to release tissue factor pathway inhibitor from endothelium. The utility of heparin and LMWH as anticancer drugs is limited due to their anticoagulant properties. Non-anticoagulant heparins can be obtained either by removing chains containing the antithrombin-binding sequence, or by inactivating critical functional groups or units of this sequence. The non-anticoagulant heparins most extensively studied are regioselectively desulfated heparins and ‘glycol-split’ heparins. Some modified heparins of both types are potent inhibitors of heparanase. A number of them also attenuate metastasis in experimental models. With cancer cells overexpressing selectins, heparin-mediated inhibition of tumor cells-platelets aggregation and tumor cell interaction with the vascular endothelium appears to be the prevalent mechanism of attenuation of early stages of metastasis. The structural requirements for inhibition of growth factors, heparanase, and selectins by heparin derivatives are somewhat different for the different activities. An N-acetylated, glycol-split heparin provides an example of application of a non-anticoagulant heparin that inhibits cancer in animal models without unwanted side effects. Delivery of this compound to mice bearing established myeloma tumors dramatically blocked tumor growth and progression.
Non-anticoagulant heparins; Cancer; Angiogenesis; Metastasis; Growth factors; Heparanase; Selectins
Low-molecular weight heparins (LMWH) appear to prolong survival of patients with cancer. Such a beneficial effect is thought to be associated with interruption of molecular mechanisms involving the heparan sulfate (HS) chains of cell surface and extracellular matrix proteoglycans (HSPG), growth factors and their receptors, heparanase, and selectins. The benefiial effects of heparin species could be associated also with their ability to release TFPA from endothelium. The utility of heparin and LMWH as anticancer drugs is limited due to their anticoagulant properties. Non anticoagulant heparins can be obtained either by removing chains containing the antithrombin-binding sequence, or by inactivating critical functional groups or units of this sequence.The non anticoagulant heparins most extensively studied are regioselectively desulfated heparins and “glycol-split” heparins. Some modified heparins of both types are potent inhibitors of heparanase. A number of them also attenuate metastasis in experimental models. With cancer cells overexpressing selectins, heparin-mediated inhibition of tumor cells-platelets aggregation and tumor cell interaction with the vascular endothelium appears to be the prevalent mechanism of attenuation of early stages of metastasis. The structural requirements for inhibition of growth factors, heparanase, and selectins by heparin derivatives are somewhat different for the different activities. An N-acetylated, glycol-split heparin provides an example of application of a non anticoagulant heparin that inhibits cancer in animal models without unwanted side effects. Delivery of this compound to mice bearing established myeloma tumors dramatically blocked tumor growth and progression.
Non anticoagulant heparins; Cancer; Angiogenesis; Metastasis; Growth Factors; Heparanase; Selectins
Interventional radiology techniques made possible by the antithrombotic properties of heparin have revolutionized treatment for a myriad of disorders. Newer low-molecular-weight heparins (LMWHs) offer several advantages over unfractionated heparin (UFH), especially in chronic settings. They are increasing in popularity for use during vascular procedures. However, LMWH shares limitations with UFH such as heterogeneity, nonspecificity, and induction of thrombocytopenia. These drawbacks have led to a search for the next generation of antithrombotic agents. Homogeneous drugs targeting specific coagulation cascade molecules are now available. The number of alternative anticoagulant drug combinations presents clinicians with a confusing array of choices. The strengths and weaknesses of UFH, LMWH, and direct antithrombin agents are presented. The promising future of LMWH and hirudins is discussed.
Heparin; low-molecular-weight heparin; interventional radiology; hirudin; bivalirudin; anticoagulation
Objective: To study the effect of unfractionated heparin (UFH) versus low molecular weight heparin (LMWH) in combination with glycoprotein (Gp) IIb/IIIa blockers on platelet activation and aggregation.
Methods: Washed platelets were stimulated with thrombin in the presence or absence of UFH (monoparin), LMWH (enoxaparin), and a Gp IIb/IIIa blocker (abciximab, eptifibatide, or tirofiban).
Results: Although Gp IIb/IIIa antagonists blocked the final common pathway of thrombin induced platelet aggregation, UFH and LMWH were better at blocking upstream platelet activation. UFH was significantly more effective than LMWH at inhibiting P selectin expression (p = 0.001) and platelet derived growth factor release from thrombin activated platelets (p = 0.012).
Conclusions: UFH and LMWH exert complementary effects to Gp IIb/IIIa blockers by inhibiting afferent pathways of platelet activation. Coadministration of heparin with Gp IIb/IIIa blockers provides improved protection against persistent platelet activation, thereby improving outcome after percutaneous coronary intervention. Judging from these data, UFH may be more effective in this regard than LMWH, at least in vitro. The use of LMWH in preference to UFH during percutaneous coronary intervention, although initially attractive, may inadequately protect against platelet activation despite the presence of Gp IIb/IIIa blockers.