Treating venous thromboembolism: enoxaparin

Population pharmacokinetics of enoxaparin in infants, children and adolescents during secondary thromboembolic prophylaxis: a cohort study

BACKGROUND

Enoxaparin has been extensively studied in adults on its safety and efficacy during prevention of symptomatic thromboembolism when acute anticoagulation or secondary prevention is required as a result of venous thrombosis or stroke. In children, it is still used off-label and little is known about the pharmacokinetics in children.

OBJECTIVES

The aim of the present study was to evaluate whether a once- or twice-daily dosing regimen would be feasible in children to achieve appropriate plasma levels of enoxaparin.

PATIENTS/METHODS

A population pharmacokinetic model was developed using anti-factor (F)Xa activity data from 126 children (median age: 5.9 years) receiving enoxaparin either as a once- or twice-daily dosing regimen.

RESULTS

A two-compartment model was adequate for describing the enoxaparin kinetics. Body weight proved to be the most predictive covariate for clearance and central volume of distribution: clearance 15 mL h⁻¹ kg⁻¹, central volume of distribution 169 mL kg⁻¹, intercompartmental clearance 58 mL h⁻¹, peripheral volume of distribution 10 L and absorption rate 0.414 h⁻¹. Interindividual variability was found to be 54% for clearance and 42% for volume of distribution.

CONCLUSION

The model is capable of describing all age groups and dosing levels of our population and predicts 12 h and 24 h enoxaparin activities sufficiently. According to our results, a once-daily enoxaparin dosing regimen with frequent monitoring is feasible. In 53.2% of the patients the median 24 h trough level was above the desired range of 0.1 IU mL⁻¹ anti-FXa activity for prophylaxis therapy.

A systematic review of economic analyses of low-molecular-weight heparin for the treatment of venous thromboembolism

INTRODUCTION

Public concerns about the increase in health care expenditure have prompted investigators to analyze the costs and benefits of health care interventions. We conducted a systematic review of economic analyses of venous thromboembolism treatment focusing on studies evaluating low-molecular-weight heparin.

MATERIALS AND METHODS

We identified studies by a MEDLINE search and a review of bibliographies of retrieved articles. From each eligible study, we extracted data on the study characteristics, the effectiveness, and the cost of managing the venous thromboembolism with respect to treatment. We critically appraised the studies according to the framework from the Users' Guides to the Medical Literature XIII: How to Use an Article on Economic Analysis of Clinical Practice.

RESULTS

Six of these eight economic analyses of venous thromboembolism treatment that met the inclusion criteria for this review showed that low-molecular-weight heparin is associated with less recurrent venous thromboembolism and is less costly than treatment with unfractionated heparin. Although discrete recurrent venous thromboembolism event rates were not included in the seventh study, these investigators concluded that the cost of low-molecular-weight heparin for the treatment of venous thromboembolism treatment was offset by the savings associated with fewer hospital admissions when low-molecular-weight heparin was used. In the eighth study, although the cost of treatment with low-molecular-weight heparin was higher than treatment with unfractionated heparin, the investigators concluded that low-molecular-weight heparin is cost-effective for inpatient management.

CONCLUSIONS

Low-molecular-weight heparin treatment may confer economic advantages over unfractionated heparin therapy because it does not require anticoagulant monitoring and it facilitates outpatient therapy.

An assessment of published pediatric dosage guidelines for enoxaparin: a retrospective review

OBJECTIVE

To evaluate the ability of published dosage guidelines for enoxaparin to achieve therapeutic anticoagulation and to determine whether the routine monitoring of anti-Xa levels is still necessary at a tertiary care pediatric institution.

METHODS

Consecutive charts and laboratory records were reviewed for all patients receiving treatment doses of enoxaparin for thrombosis in the authors institution over a 4-year period (1998-2002).

RESULTS

Sixty-six percent (25/38) of the anti-Xa levels were within the recommended therapeutic range (0.5-1.0 [+/- 10%] U/mL) after two doses. The success rates of achieving therapeutic levels were 1/6, 2/3, 6/9, 10/11, and 6/9, for patients 2 months or younger, more than 2 months to 1 year, more than 1 year to 6 years, more than 6 years to 12 years, and more than 12 years of age, respectively. Patients with cardiac or renal disease were more likely to achieve high anti-Xa levels. Thirty-seven percent of patients reported adverse effects. The most common effects were injection site-related bruising and minor bleeding. One patient experienced a major bleed that was not life-threatening.

CONCLUSIONS

Most patients achieved therapeutic anticoagulation when dosed according to the published guidelines. Children with cardiac conditions or renal insufficiency or those younger than 2 months were more likely to require dosage adjustments to achieve the therapeutic range. Routine monitoring of anti-Xa levels is still necessary in these patient populations, particularly when the early establishment of therapeutic anticoagulation may be critical. Enoxaparin appears to be well tolerated in the authors' patient population.