The role of low-molecular-weight heparin in the management of acute coronary syndromes

Mean Activated Clotting Time of Patients Receiving Intravenous Heparin and Undergoing Primary Percutaneous Coronary Intervention for ST Elevation Myocardial Infarction

Introduction The most prevalent cause of death is acute myocardial infarction (AMI). Primary percutaneous coronary intervention (PPCI) has replaced thrombolysis as the recommended therapeutic option for individuals with ST-segment elevation myocardial infarction (STEMI). However, more effective anticoagulation regimes are required for PCI due to the limitations of unfractionated heparin. Objective This study aimed to ascertain the connection between the mean activated clotting time and the risk of bleeding and infarcts in individuals receiving intravenous heparin during PPCI for STEMI. Methods This was a one-year prospective observational study carried out at the National Institute of Cardiovascular Diseases (NICVD), Karachi, Pakistan. Results The majority (70.15%) were male, with a mean age of 56.08 ± 8.92 years. Following PPCI, the average active clotting time (ACT) was 350.56 ± 39.62 seconds (range 255 to 453), compared to the pre-PPCI mean of 504.15 ± 38.98 seconds. ACT was considerably higher in female patients, smokers, and overweight patients. The mean ACT was not significantly higher in patients with hypertension (HTN) and dyslipidemia (DLD). Conclusion The ACT range in this investigation was 255 to 453 seconds, and there was no discernible relationship between ACT readings and problems related to bleeding and ischemia. To determine who is more at risk, bleeding risk models should be used and improved further before catheterization.

Safety and Efficacy of Low Molecular Weight Heparin for Thromboprophylaxis in the Elderly: A Network Meta-Analysis of Randomized Clinical Trials

Background: Given their changing pathophysiology, elderly patients carry a high risk of embolism and bleeding events; hence, use of appropriate anticoagulants is very important. Low molecular weight heparin (LMWH) is one of the most widely used anticoagulants although LMWHs differ in their anti-Xa, antithrombin, and anticoagulant activities. To date, no study has directly compared the safety and efficacy of different LMWHs in the elderly. We aimed to compare such differences by conducting a network meta-analysis.

Methods: We searched the Pubmed, Embase, and Cochrane databases for randomized controlled trials (RCTs) of LMWHs that included patients ≥60 years old up to July 22, 2020. Safety outcomes included venous thromboembolism (VTE) or VTE-related death, deep thrombus embolism, and pulmonary embolism. Safety outcomes were clinically relevant bleeding, major bleeding, minor bleeding, and all-cause death. We calculated relative ratios (RR) and 95% confidence intervals (CI) for all outcomes. The cumulative ranking probabilities (SUCRA) were conducted to rank the comparative effects and safety of all LMWHs.

Results: We included 27 RCTs (30,441 elderly), comprising five LMWHs. LMWH was more effective than placebo in preventing VTE or VTE-related death (RR 0.36, 95% CI 0.25–0.53) but less effective than a novel oral anticoagulant (RR 1.59, 95% CI 1.33–1.91) and safer than acenocoumarol regarding risk of clinically relevant bleeding (RR 0.67, 95% CI 0.49–0.90). However, indirect comparison of efficacy and safety of the five LMWHs showed no significant difference in our network analysis, and the subgroup analyses (such as in patients with deep venous thrombosis, cardiac disease, or age >65 years old) supported the results. The SUCRA showed that tinzaparin performed best in preventing VTE or VTE-related death (SUCRA 68.8%, cumulative probability 42.3%) and all-cause death (SUCRA 84.2%, cumulative probability 40.7%), whereas nadroparin was predominant in decreasing the risk of clinically relevant bleeding (SUCRA 84.8%, cumulative probability 77.0%).

Conclusions: On present evidence, there are no significant differences in the efficacy and safety of different LMWHs for the elderly. According to the rank probability analysis, nadroparin seems to be safer for the elderly with a high risk of bleeding, whereas tinzaparin is more effective for those with low bleeding risk.

Unfractionated Heparin with Sequential Enoxaparin in Patients with Complex Coronary Artery Lesions during Percutaneous Coronary Intervention

Background:

Unfractionated heparin (UFH), despite its limitations, has been used as the primary anticoagulant alternative during the percutaneous coronary intervention (PCI). Some studies indicated that intravenous enoxaparin could be an effective and safe option. Our team used enoxaparin alone at one time according to the guidelines (Class IIA) and found a little catheter thrombosis during PCI. We recommend a new anticoagulation strategy using enoxaparin in combination with UFH. Enoxaparin has a more predictable anticoagulant response with no need of repeatedly monitoring anticoagulation during PCI. This retrospective study aimed to evaluate the efficacy and safety of using enoxaparin in combination with UFH in PCI patients with complex coronary artery disease.

Methods:

Between January 2015 and April 2017, 600 PCI patients who received intravenous UFH at an initial dose of 3000 U plus intravenous enoxaparin at a dose of 0.75 mg/kg (observation group) and 600 PCI patients who received UFH at a dose of 100 U/kg (control group) were consecutively included in this retrospective study. The endpoints were postoperative 48-h thrombolysis in myocardial infarction (TIMI) bleeding and transfusion and 30-day and 1-year major adverse cardio-cerebrovascular events (MACCE).

Results:

Baseline clinical, angiographic, and procedural characteristics were similar between groups, except there was less stent implantation per patient in the observation group (2.13 vs. 2.25 in the control group, P = 0.002). TIMI bleeding (3.3% vs. 4.7%) showed no significant difference between the observation group and control group. During the 30-day follow-up, the rate of MACCE was 0.9% in the observation group and 1.5% in the control group. There was no significant difference in the rates of MACCE, death, myocardial infarction, target vessel revascularization, cerebrovascular event, and angina within 30 days and 1 year after PCI between groups as well as in the subgroup analysis of transfemoral approach.

Conclusions:

UFH with sequential enoxaparin has similar anticoagulant effect and safety as UFH in PCI of complex coronary artery disease.

Comparison of bleeding complications and one-year survival of low molecular weight heparin versus unfractioned heparin for acute myocardial infarction in elderly patients. The FAST-MI registry

BACKGROUND

There are limited data on the safety and efficacy of low molecular weight heparin (LMWH) in elderly patients with acute myocardial infarction (AMI).

METHODS

We aimed to compare LMWH with unfractioned heparin (UFH) in the management of AMI in elderly patients. FAST-MI is a nationwide registry carried out over a 1-month period in 2005, including consecutive patients with AMI admitted to intensive care unit <48 h from symptom onset in 223 participating centers. We assessed the impact of LMWH on bleeding, the need for blood transfusion and one-year survival in elderly patients (≥ 75 years).

RESULTS

963 patients treated with heparin were included (mean age 82 ± 5 years; 51% women; 42.5% ST-elevation myocardial infarction). Major bleeding (2.4% vs. 6.1%, P=0.004) and blood transfusions (4.6% vs. 9.7%, P=0.002) were significantly less frequent with LMWH compared with the UFH, a difference that persisted after multivariate adjustment (OR=0.41, 95% CI: 0.20-0.83 and OR=0.49, 95% CI: 0.28-0.85, respectively). One-year survival and stroke and reinfarction-free survival were also significantly higher with LMWH compared with UFH (OR=0.66, 95% CI: 0.50-0.85 and OR=0.71, 95% CI: 0.56-0.91, respectively). In two cohorts of patients matched on a propensity score for getting LMWH and with similar baseline characteristics (328 patients per group), major bleeding and transfusion were significantly lower while one-year survival was significantly higher in patients receiving LMWH.

CONCLUSIONS

The present data show that in elderly patients admitted for AMI, use of LMWH is associated with less bleeding, less need for transfusion, and higher survival, compared with the use of UFH.

[Enoxaparin vs. non-fractionated heparin in primary angioplasty of acute myocardial infarction]

OBJECTIVE

The objective of this study is to compare the effectiveness of intravenous enoxaparin (ENX) and Non-fractionated Heparin (NFH) in primary angioplasty (PA) of acute myocardial infarction (PA-AMI).

DESIGN

A prospective, observational study.

PATIENTS AND METHODS

A total of 191 patients admitted at the hospital with the diagnosis of Acute Myocardial Infarction (AMI) and treated with primary angioplasty were included. ENX was used in 91 patients (47.6%) and NFH in 100 patients (52.4%). Choice of treatment was based on the operator's opinion. Patients with cardiogenic shock were excluded. The first group received an intravenous bolus of ENX (0.75-1 mg/Kg) and the second one NFH (70-100 u/Kg), depending on whether it was associated with abciximab or not. In-hospital follow-up was performed, evaluating mortality and bleeding complications of both treatments.

RESULTS

In-hospital mortality was 1.1% for the ENX group and 3.3% for NFH one. No significant differences were found in the number of bleeding complications with ENX (4.4%) and NFH (9.0%). There was one subacute thrombosis of stent for the ENX group and 3 thrombosis in the NFH-treated group. No significant differences were found in size of infarction measure with troponin I level (63.1 for ENX and 54.8 for the NFH) or in the left ventricle ejection fraction on hospital discharge (51% for ENX and 49.4% for the NFH).

CONCLUSIONS

Primary angioplasty can be safely sued with the intravenous administration of ENX, no significant differences being found between both treatments in mortality and bleeding complications.

An endogenously deposited fibrin scaffold determines construct size in the surgically created arteriovenous loop chamber model of tissue engineering

BACKGROUND

An arteriovenous loop (AVL) enclosed in a polycarbonate chamber in vivo, produces a fibrin exudate which acts as a provisional matrix for the development of a tissue engineered microcirculatory network.

OBJECTIVES

By administering enoxaparin sodium - an inhibitor of fibrin polymerization, the significance of fibrin scaffold formation on AVL construct size (including the AVL, fibrin scaffold, and new tissue growth into the fibrin), growth, and vascularization were assessed and compared to controls.

METHODS

In Sprague Dawley rats, an AVL was created on femoral vessels and inserted into a polycarbonate chamber in the groin in 3 control groups (Series I) and 3 experimental groups (Series II). Two hours before surgery and 6 hours post-surgery, saline (Series I) or enoxaparin sodium (0.6 mg/kg, Series II) was administered intra-peritoneally. Thereafter, the rats were injected daily with saline (Series I) or enoxaparin sodium (1.5 mg/kg, Series II) until construct retrieval at 3, 10, or 21 days. The retrieved constructs underwent weight and volume measurements, and morphologic/morphometric analysis of new tissue components.

RESULTS

Enoxaparin sodium treatment resulted in the development of smaller AVL constructs at 3, 10, and 21 days. Construct weight and volume were significantly reduced at 10 days (control weight 0.337 +/- 0.016 g [Mean +/- SEM] vs treated 0.228 +/- 0.048, [P < .001]: control volume 0.317 +/- 0.015 mL vs treated 0.184 +/- 0.039 mL [P < .01]) and 21 days (control weight 0.306 +/- 0.053 g vs treated 0.198 +/- 0.043 g [P < .01]: control volume 0.285 +/- 0.047 mL vs treated 0.148 +/- 0.041 mL, [P < .01]). Angiogenesis was delayed in the enoxaparin sodium-treated constructs with the absolute vascular volume significantly decreased at 10 days (control vascular volume 0.029 +/- 0.03 mL vs treated 0.012 +/- 0.002 mL [P < .05]).

CONCLUSION

In this in vivo tissue engineering model, endogenous, extra-vascularly deposited fibrin volume determines construct size and vascular growth in the first 3 weeks and is, therefore, critical to full construct development.

Enoxaparin versus unfractionated heparin in elective percutaneous coronary intervention

BACKGROUND

Despite its limitations, unfractionated heparin has been the standard anticoagulant used during percutaneous coronary intervention (PCI). Several small studies have suggested that intravenous enoxaparin may be a safe and effective alternative. Our primary aim was to assess the safety of enoxaparin as compared with that of unfractionated heparin in elective PCI.

METHODS

In this prospective, open-label, multicenter, randomized trial, we randomly assigned 3528 patients with PCI to receive enoxaparin (0.5 or 0.75 mg per kilogram of body weight) or unfractionated heparin adjusted for activated clotting time, stratified according to the use or nonuse of glycoprotein IIb/IIIa inhibitors. The primary end point was the incidence of major or minor bleeding that was not related to coronary-artery bypass grafting. The main secondary end point was the percentage of patients in whom the target anticoagulation levels were reached.

RESULTS

Enoxaparin at a dose of 0.5 mg per kilogram was associated with a significant reduction in the rate of non-CABG-related bleeding in the first 48 hours, as compared with unfractionated heparin (5.9% vs. 8.5%; absolute difference, -2.6; 95% confidence interval [CI], -4.7 to -0.6; P=0.01), but the higher enoxaparin dose was not (6.5% vs. 8.5%; absolute difference, -2.0; 95% CI, -4.0 to 0.0; P=0.051). The incidence of major bleeding was significantly reduced in both enoxaparin groups, as compared with the unfractionated heparin group. Target anticoagulation levels were reached in significantly more patients who received enoxaparin (0.5-mg-per-kilogram dose, 79%; 0.75-mg-per-kilogram dose, 92%) than who received unfractionated heparin (20%, P<0.001).

CONCLUSIONS

In elective PCI, a single intravenous bolus of 0.5 mg of enoxaparin per kilogram is associated with reduced rates of bleeding, and a dose of 0.75 mg per kilogram yields rates similar to those for unfractionated heparin, with more predictable anticoagulation levels. The trial was not large enough to provide a definitive comparison of efficacy in the prevention of ischemic events. (ClinicalTrials.gov number, NCT00077844 [ClinicalTrials.gov].).

The use of a HEMOCHRON JR. HEMONOX point of care test in monitoring the anticoagulant effects of enoxaparin during interventional coronary procedures

BACKGROUND

Enoxaparin is increasingly used for the anticoagulation of patients undergoing percutaneous coronary intervention (PCI). Several reports have suggested the utility of using point of care tests in monitoring the anticoagulation levels of enoxaparin in patients undergoing PCI. The objective of this study was to evaluate a new point-of-care test (POCT) HEMONOX in monitoring the anticoagulant effect of enoxaparin in non citrated fresh whole blood samples from patients undergoing elective PCI procedure.

METHODS

Following IRB approval, blood samples were obtained from fifty-four patients who received two sequential intravenous doses of enoxaparin; 0.1 mg/kg followed 5 min later by 0.4 mg/kg for a total of 0.5 mg/kg. Blood was drawn at baseline and at 5, 10, 30 and 60 min post first bolus for evaluation in the clot-based POCT HEMONOX, ACT and aPTT and the chromogenic anti-Xa activity assay.

RESULTS

HEMONOX clotting time (CT) at baseline was 62.6 +/- 6.2 secs, (n = 32) in healthy donors and statistically higher in PCI patients (71.6 +/- 9.1 secs, p = 0.0001). The peak HEMONOX response that was always achieved at 10 min post bolus was >100 secs in all 54 patients, of these 83% yielded CT >150 secs (range: 150-466). There was no detectable anti-Xa activity level at baseline while peak HEMONOX CT corresponded to therapeutic levels (0.85 +/- 0.14 U/ml; range: 0.61-1.34). Both HEMONOX CT and anti-Xa level significantly decreased at the time of sheath removal. HEMONOX CT at peak response suggested 3 patient subgroups with different levels of sensitivity to enoxaparin: low, intermediate and high responders. The correlation between anti-Xa activity level and HEMONOX CT was >or=0.85 in each patient subgroup when data from the 3 critical time points; baseline (absence of drug), peak response (10 min post bolus) and sheath removal (60 min post bolus) were analyzed. The correlation diminished to >or=0.83 when the analyses included data from all 5 time points [baseline, 5, 10, 30, and 60 min post bolus]. The HEMONOX test was the most sensitive POCT to measure the anticoagulant effects of enoxaparin. All patients completed PCI successfully.

CONCLUSION

The HEMONOX test may be able to guide anticoagulation with enoxaparin during PCI. The HEMONOX assay is a one step whole blood coagulation test performed on the HEMOCHRON Jr. Signature + POC system. The method was evaluated to monitor the anticoagulant level of enoxaparin in blood samples from patients undergoing PCI after receiving an intravenous dose of 0.5 mg/kg. The results suggest a clear distinction of HEMONOX CT between the baseline value of untreated patients and patients achieving therapeutic enoxaparin levels.

Oral heparin delivery: Design and in vivo evaluation of a stomach-targeted mucoadhesive delivery system

Low molecular weight heparin (LMWH) is an agent of choice in the anti-coagulant therapy and prophylaxis of thrombosis and coronary syndromes. However, the therapeutic use is partially limited due to a poor oral bioavailability. It was therefore the aim of this study to design and evaluate a highly efficient stomach-targeted oral delivery system for LMWH. In order to appraise the influence of the molecular weight on the oral bioavailability, mini-tablets comprising 3 kDa (279 IU) and 6 kDa (300 IU) LMWH, respectively, were generated and tested in vivo in rats. The potential of the test formulations based on thiolated polycarbophil, was evaluated in comparison to hydroxyethylcellulose (HEC) as control carrier matrix. The plasma levels of LMWH after oral versus subcutaneous administration were determined in order to calculate the relative bioavailability. With the delivery system containing 3 kDa LMWH (279 IU) a relative bioavailability of 19.1% was achieved, offering a significantly (p < 0.05) better bioavailability than the control system displaying a relative bioavailability of 8.1% The 6 kDa LMWH (300 IU) formulation displayed a relative bioavailability of 10.7% in contrast to the control displaying a relative bioavailability of 2.1%. In conclusion, these results suggest that mucoadhesive thiolated polymers are a promising tool for the non-invasive stomach-targeted systemic delivery of LMWH as model for a hydrophilic macromolecular polysaccharide.

Guidelines for percutaneous coronary interventions. The Task Force for Percutaneous Coronary Interventions of the European Society of Cardiology

In patients with stable CAD, PCI can be considered a valuable initial mode of revascularization in all patients with objective large ischaemia in the presence of almost every lesion subset, with only one exception: chronic total occlusions that cannot be crossed. In early studies, there was a small survival advantage with CABG surgery compared with PCI without stenting. The addition of stents and newer adjunctive medications improved the outcome for PCI. The decision to recommend PCI or CABG surgery will be guided by technical improvements in cardiology or surgery, local expertise, and patients' preference. However, until proved otherwise, PCI should be used only with reservation in diabetics with multi-vessel disease and in patients with unprotected left main stenosis. The use of drug-eluting stents might change this situation. Patients presenting with NSTE-ACS (UA or NSTEMI) have to be stratified first for their risk of acute thrombotic complications. A clear benefit from early angiography (<48 h) and, when needed, PCI or CABG surgery has been reported only in the high-risk groups. Deferral of intervention does not improve outcome. Routine stenting is recommended on the basis of the predictability of the result and its immediate safety. In patients with STEMI, primary PCI should be the treatment of choice in patients presenting in a hospital with PCI facility and an experienced team. Patients with contra-indications to thrombolysis should be immediately transferred for primary PCI, because this might be their only chance for quickly opening the coronary artery. In cardiogenic shock, emergency PCI for complete revascularization may be life-saving and should be considered at an early stage. Compared with thrombolysis, randomized trials that transferred the patients for primary PCI to a 'heart attack centre' observed a better clinical outcome, despite transport times leading to a significantly longer delay between randomization and start of the treatment. The superiority of primary PCI over thrombolysis seems to be especially clinically relevant for the time interval between 3 and 12 h after onset of chest pain or other symptoms on the basis of its superior preservation of myocardium. Furthermore, with increasing time to presentation, major-adverse-cardiac-event rates increase after thrombolysis, but appear to remain relatively stable after primary PCI. Within the first 3 h after onset of chest pain or other symptoms, both reperfusion strategies seem equally effective in reducing infarct size and mortality. Therefore, thrombolysis is still a viable alternative to primary PCI, if it can be delivered within 3 h after onset of chest pain or other symptoms. Primary PCI compared with thrombolysis significantly reduced stroke. Overall, we prefer primary PCI over thrombolysis in the first 3 h of chest pain to prevent stroke, and in patients presenting 3-12 h after the onset of chest pain, to salvage myocardium and also to prevent stroke. At the moment, there is no evidence to recommend facilitated PCI. Rescue PCI is recommended, if thrombolysis failed within 45-60 min after starting the administration. After successful thrombolysis, the use of routine coronary angiography within 24 h and PCI, if applicable, is recommended even in asymptomatic patients without demonstrable ischaemia to improve patients' outcome. If a PCI centre is not available within 24 h, patients who have received successful thrombolysis with evidence of spontaneous or inducible ischaemia before discharge should be referred to coronary angiography and revascularized accordingly--independent of 'maximal' medical therapy.

Low-molecular-weight heparins in ischemic heart disease

PURPOSE OF REVIEW

The objective of this review was to summarize the recent developments regarding the use of low-molecular-weight heparins in the management of acute coronary syndromes.

RECENT FINDINGS

In the setting of unstable angina and non-ST-elevation myocardial infarction, enoxaparin is superior to unfractionated heparin in reducing death, myocardial infarction, and recurrent ischemia both in the short-term and to 1 year. However, this does not necessarily imply a class effect of low-molecular-weight heparins in general. When combined with glycoprotein IIb/IIIa inhibitors, enoxaparin appears to be effective and safe even for patients treated according to an early invasive strategy. In patients receiving fibrinolytics for ST-elevation myocardial infarction, low-molecular-weight heparins are as effective as unfractionated heparin in maintaining patency of the infarct-related artery and in reducing the composite endpoint of death and reinfarction. However, serious bleeding is more common, especially among the elderly, and the optimal dosing regimen in ST-elevation myocardial infarction remains to be defined.

SUMMARY

Low-molecular-weight heparins are safe and effective in the management of unstable angina and non-ST-elevation myocardial infarction, with or without concurrent administration of glycoprotein IIb/IIIa inhibitors. Ongoing studies will clarify the role of low-molecular-weight heparins as adjunctive therapy for fibrinolysis.

Pharmacokinetics and pharmacodynamics of argatroban in combination with a platelet glycoprotein IIB/IIIA receptor antagonist in patients undergoing percutaneous coronary intervention

The pharmacokinetic-pharmacodynamic (PK-PD) relationship of argatroban, administered in combination with a platelet glycoprotein IIb/IIIa receptor antagonist, was characterized in patients undergoing percutaneous coronary intervention (PCI). Plasma argatroban and activated clotting times (ACTs) were assessed periprocedurally in 152 patients administered argatroban (250- or 300-microg/kg bolus, then 15-microg/kg/min infusion) in combination with abciximab or eptifibatide during PCI. The PK and PK-PD models were developed utilizing a sequential population approach in NONMEM. Population PK estimates for clearance, central volume, and peripheral volume were 22.0 L/h, 11.0 L, and 13.0 L, respectively (coefficients of variation [CVs] </= 10%). By covariate analysis, clearance increased linearly with body weight. Plasma argatroban and ACT effect were well described using a sigmoidal E(max) model. For argatroban in combination with platelet glycoprotein IIb/IIIa receptor blockade in patients undergoing PCI, population PK parameters are consistent with values reported for argatroban in healthy subjects. A predictable relationship exists between argatroban concentration and effect in this setting.

Acute Catheterization and Urgent Intervention Triage strategY (ACUITY) trial: study design and rationale

BACKGROUND

Patients with acute coronary syndromes (ACS; unstable angina and non-ST-segment elevation myocardial infarction) are at significant risk for death and myocardial infarction. Early angiography followed by revascularization is considered the treatment of choice for moderate- to high-risk patients with ACS. However, despite the integration of newer therapies including stents, glycoprotein IIb/IIIa inhibitors, and thienopyridines, the rate of adverse ischemic events still remains unacceptably high, and the intensive pharmacologic regimens used to stabilize the disrupted atherosclerotic plaque and support angioplasty and surgical revascularization procedures elicit a high rate of bleeding complications. Pilot trials suggest that the thrombin-specific anticoagulant bivalirudin may improve clinical outcomes in ACS.

STUDY DESIGN

In the Acute Catheterization and Urgent Intervention Triage strategY (ACUITY) trial, 13,800 patients with moderate- to high-risk ACS are being prospectively randomly assigned at up to 600 centers to unfractionated heparin or enoxaparin + IIb/IIIa inhibition, versus bivalirudin + IIb/IIIa inhibition, versus bivalirudin + provisional IIb/IIIa inhibition. All patients undergo cardiac catheterization within 72 hours, followed by percutaneous or surgical revascularization when appropriate. In a second random assignment, patients assigned to receive IIb/IIIa inhibitors are subrandomized to upstream drug initiation, versus IIb/IIIa inhibitor administration during angioplasty only. The primary study end point is the composite of death, myocardial infarction, unplanned revascularization for ischemia, and major bleeding at 30 days. Clinical follow-up will continue for 1 year.

CONCLUSIONS

The ACUITY trial is the largest study yet performed in patients with ACS undergoing an invasive strategy. In addition to evaluating the utility of bivalirudin in ACS, this study will also provide important guidance regarding the necessity for and timing of IIb/IIIa inhibitor administration.

Chain length-dependent effects of alkylmaltosides on nasal absorption of enoxaparin

The purpose of this study was to investigate whether the hydrophobic chain length of alkylmaltosides affects their efficacy as absorption promoters for nasally administered low-molecular-weight heparin and to study whether these agents enhance nasal absorption in a time-dependent manner without causing irreversible damage to the nasal epithelial membrane. For the nasal absorption studies, enoxaparin formulated with different alkylmaltosides was administered nasally to anesthetized rats and absorption of the drug was determined by measuring plasma anti-factor Xa activity. Reversibility studies were performed by administering enoxaparin at different time points after administration of alkylmaltosides. The AUC(0-360) for plasma anti-factor Xa-time curves increased with the increase in alkylmaltoside concentration in the formulations. Absolute and relative bioavailability of enoxaparin were increased by two-fold when the alkyl chain length of maltosides was increased from 8 to 14 carbons. Alkylmaltosides therefore increase nasal absorption of enoxaparin in a dose- and chain length-dependent manner. Of the alkylmaltosides tested, tetradecylmaltoside is the most potent enhancer of nasal absorption of enoxaparin. Longer chain alkylmaltosides produce a more prolonged effect on nasal mucosa compared with those with shorter alkyl chain.

Low molecular weight heparin and atherosclerosis

Low molecular weight heparin (LMWH) has dramatically impacted the treatment of venous thromboembolic disease and acute coronary syndromes. Recent studies help define the role of these agents for patients undergoing percutaneous coronary interventions and for patients treated with thrombolytic agents for ST-segment elevation myocardial infarction. Recent studies also suggest potential usefulness of LMWH for patients with peripheral vascular disease and its limits of utility in stroke. This review summarizes the evidence about the use of LMWH in these clinical situations.