Laboratory monitoring of low-molecular-weight heparin therapy--part II. Monitoring LMWH therapy? For the moment a non-question

Factor Xa Levels in Patients Receiving Prophylactic Enoxaparin Sodium in the Intensive Care Unit of an Academic Hospital

Background: The aim of this study was to determine the anti-factor Xa levels in patients receiving enoxaparin sodium for venous thromboembolism prophylaxis in the intensive care unit (ICU).

Patients and methods: Using a cross-sectional study methodology, 73 ICU patients receiving 40 mg enoxaparin sodium daily were enrolled in this study. Anti-factor Xa levels were measured following the second dose. Prophylactic and subprophylactic groups of patients were compared for age, sex, weight, body mass index, total bilirubin, serum albumin, and APACHE II score.

Results: Anti-factor Xa levels were prophylactic (0.2–0.6 IU/mL) in 44 (60.3%) patients and subprophylactic (<0.2 IU/mL) in 29 (39.7%) patients. The mean (SD) actual delivered dose of enoxaparin per kilogram body weight was significantly higher, at 0.59 (0.11) mg/kg in the prophylactic group compared to 0.53 (0.13) mg/kg in the subprophylactic group (p = 0.043). The subprophylactic group had significantly lower serum albumin levels compared to the prophylactic group. The total bilirubin levels were not found to be significantly different between the two groups (p = 0.110).

Conclusion: A fixed prophylactic 40 mg dose of enoxaparin was associated with a high proportion of subprophylactic anti-factor Xa levels. Weight-based dose and serum albumin level were independent predictors of achieving the prophylactic target range.

How to cite this article: Baloo MM, Scribante J, Perrie H, Calleemalay D, Omar S. Factor Xa Levels in Patients Receiving Prophylactic Enoxaparin Sodium in the Intensive Care Unit of an Academic Hospital. Indian J Crit Care Med 2021;25(8):917–919.

Pharmacodynamics assessment of Bemiparin after multiple prophylactic and single therapeutic doses in adult and elderly healthy volunteers and in subjects with varying degrees of renal impairment

INTRODUCTION

Aging and renal impairment may prolong the half-life and lead to accumulation of low molecular weight heparins. Correct dosing is critical to prevent bleeding or thrombosis.

MATERIALS AND METHODS

Open, parallel study. Healthy adult [n=13] and elderly (>65yrs) [n=12] volunteers; and subjects with mild (ClCr≥50 to ≤80mL/min, n=8), moderate (ClCr≥30 to <50mL/min, n=7), and severe (ClCr<30mL/min, n=8) renal impairment received four prophylactic doses (3,500IU/24h) and a single therapeutic dose (115IU/kg) of bemiparin with an interim washout period. Anti-FXa activity and the potential need for dose adjustment were evaluated.

RESULTS

There were statistically significant differences in the severe renal impairment group vs. adult volunteers in all anti-FXa related parameters, but no significant differences in any of the anti-FXa related parameters between the adult and the elderly. Anti-FXa simulations after 10 prophylactic doses predicted mean Amax=0.59IU/mL in subjects with severe renal impairment and 0.33-0.39IU/mL in the rest. Simulations in the severe renal impairment group with dose adjustment (2,500IU/24h) predicted all individual Amax<0.60IU/mL (mean Amax=0.42IU/ml). Simulations after 10 therapeutic doses predicted mean Amax=1.22IU/mL in severe renal impairment group and 0.89-0.98IU/mL in the rest. Simulations in the severe renal impairment group with 75% dose adjustment predicted individual Amax≤1.60IU/mL (mean Amax=0.91IU/mL).

CONCLUSIONS

No dose adjustments are required in elderly with preserved renal function. A dose adjustment of bemiparin is only advisable in patients with severe renal impairment when using prophylactic or therapeutic doses.

Effects of enoxaparin preparations on thrombin generation and their correlation with their anti-FXa activity

OBJECTIVE

Anticoagulant effect of LMWHs is monitored by anti-factor Xa (anti-FXa) activity assay. Since this test has several limitations, the aim of this study was to explore the activity of two LMWHs by thrombin generation assay (TG, which presents an overall picture of hemostatic balance) and its correlation with their anti-FXa activity.

METHODS

In an open-label, randomized cross-over study, 40  mg of two enoxaparins, the original branded formulation (R) and another one, also marketed in Argentina (T), were daily injected subcutaneously, for 7 days, to 20 healthy volunteers, with a 7-day washout interval. Blood samples were collected before treatment and 180  minutes after the injection on days 3 and 7. TG in platelet-poor plasma activated with tissue factor was assessed by lag time (LT), time to peak (TTP), peak (PTG), and endogenous thrombin potential (ETP). Anti-FXa and anti-FIIa activities, free tissue factor pathway inhibitor (free TFPI), tissue plasminogen activator (t-PA), plasminogen activator inhibitor type 1 (PAI-1), and euglobulin lysis time (ELT) were also assayed.

RESULTS

The mean (SD) anti-FXa (UI/ml) for T and R increased on days 3 and 7. LT and TTP were significantly prolonged by both LMWHs, with no differences between them. The mean ETP (nmol/L) for T and R at 3 and 7 days after treatment were significantly reduced when compared with basal values (p = 0.001 for all). On day 3, a significant correlation was shown between the variables describing TG and anti-FXa for T and R, without differences between them, for LT (r: 0.516 and 0486), ETP (r: 0.532 and 0.574), PEAK (r: 0.482 and 0.501), and TTP (r: 0.577 and 0.503), respectively. This correlation was also significant on day 7. Anti-FIIa activity and free TFPI increased significantly at 3 and 7 days for both LMWHs, without differences between them. R and T decreased ELT and PAI-1, but had no effect on t-PA. There were no differences between both LMWHs in routine hemostatic tests. No adverse events were reported.

CONCLUSIONS

Correlation between TG and anti-FXa activity was good. Both enoxaparins induced similar change of coagulation parameters, with a significant increase in fibrinolytic activity.

Study of bioaccumulation of dalteparin at a prophylactic dose in patients with various degrees of impaired renal function

BACKGROUND

Low-molecular-weight heparins (LMWH) have been shown to be effective and safe for prophylaxis of thromboembolic diseases. However, issues regarding safety and optimal use of LMWH arise in patients with renal insufficiency (RI).

OBJECTIVES

To compare pharmacokinetic data of dalteparin for up to 3 weeks in patients with various degrees of RI.

PATIENTS AND METHODS

Patients from general medical and surgical wards were included in this prospective cohort study and divided into three groups according to renal function: A=normal (GFR>or=60 mL min(-1)1.73 m(-2)), B=mild RI (GFR 30-59 mL min(-1)1.73 m(-2)), C=severe RI (GFR<30 mL min(-1)1.73 m(-2)). Dalteparin was injected s.c. once daily at a prophylactic dose. Peak anti-Xa activity levels (anti-Xa) were measured 4+/-1 h after injection on day 1 and every third day up to 3 weeks. Primary objectives were peak anti-Xa levels and adjusted anti-Xa levels, adjustment being carried out for dose and body weight.

RESULTS

A total of 42 patients could be analyzed during a median of 10 days (interquartile range IQR 4-13, range 1-20). In all groups, adjusted peak anti-Xa levels were not different on day 10 compared with day 1. No bioaccumulation>30% could be found up to day 10 even in patients with severe RI.

CONCLUSION

The use of dalteparin at a prophylactic dose was not associated with a bioaccumulation>30% even in patients with severe renal insufficiency during a median follow-up of 10 days (IQR 4-13, range 1-20).

Biomarkers and coagulation tests for assessing the biosimilarity of a generic low-molecular-weight heparin: results of a study in healthy subjects with enoxaparin

Low-molecular-weight heparins (LMWHs) differ considerably in their influence on clotting tests and release of tissue factor pathway inhibitor (TFPI). Biosimilarity therefore becomes an issue when generic forms of LMWHs are developed. So far, no bioequivalence study with a generic LMWH has been reported. A generic enoxaparin (test) was compared with the originator (reference) in 20 volunteers after single-dose subcutaneous administration (40 mg enoxaparin sodium, 4000 IU/mL anti-factor Xa (anti-FXa; activity). Target variables were anti-FXa and anti-FIIa activity, activated partial thromboplastin time (aPTT), prothrombinase-induced clotting time (PiCT), and TFPI over 24 hours. The statistical evaluation of the anti-FXa activity profile demonstrated bioequivalence of test and reference with confidence intervals of area under the plasma concentration-time curve (AUC0-tlast) (93%-99%) and Amax (88%-95%). Confidence intervals of AUC(0-tlast) (89%-102%) and Amax (90%-103%) of anti-FIIa activity also fulfill bioequivalence criteria. The 90% confidence interval for the maximum concentration of TFPI ranged from 90% to 113%. The claim of similarity was also supported by aPTT and PiCT profiles. Bioequivalence with the originator enoxaparin could be demonstrated by ex vivo inhibition of FXa and FIIa activity, by coagulation tests (aPTT and PiCT), and by in vivo release of TFPI. Whether such data also prove biosimilarity of the generic enoxaparin needs to be determined.