The dose proportionality of the pharmacokinetics of ardeparin, a low molecular weight heparin, in healthy volunteers

High-dose Intravenous Dalteparin Can be Monitored Effectively Using Standard Coagulation Times

The objective of this study was to examine the pharmacokinetics of intravenous dalteparin (Fragmin, Pharmacia-Upjohn, Peapack, NJ) and to assess the accuracy of standard coagulation-based monitoring techniques as an estimate of drug concentration with which to guide dosing. Knowledge of the kinetic behavior of low-molecular-weight heparins (LMWHs) and the possible utility of coagulation times for monitoring may aid in the development of safe and effective dosing algorithms for percutaneous coronary interventions. Twenty normal volunteers were treated at 2-week intervals with each of three intravenous dalteparin doses. Measurement of anti-IIa, anti-Xa, activated partial thromboplastin time (aPTT), activated clotting time (ACT), and low-range ACT was performed at baseline and at seven additional time points over 8 hours. The half-life of intravenous dalteparin is 77 minutes with slight dose-related variation. The aPTT, LR-ACT, and standard ACT are prolonged after dalteparin administration with the increase closely correlated to anti-Xa activity (aPTT, r = 0.85; LR-ACT, r = 0.79). Classification of anticoagulation intensity range using aPTT or LR-ACT in comparison to anti-Xa activity (0.5-0.99, 1.0-1.49, 1.5-2, >2) displays a level of agreement (kappa: aPTT = 0.69, LR-ACT = 0.59) that is comparable to values reported for coagulation time guidance of unfractionated heparin administration. Standard coagulation times are sensitive to the anticoagulant effect of dalteparin with a degree of correlation that suggests their utility for estimating drug concentration during high dose therapy. Trials establishing a relationship between monitoring and clinical efficacy, and the risk/reward of different treatment ranges alone or in combination with GPIIb/IIIa inhibitors and clopidogrel, are necessary.

Pharmacokinetics and pharmacodynamics of low-molecular-weight heparins and glycoprotein IIb/IIIa receptor antagonists in renal failure

Data regarding the use of low-molecular-weight heparins (LMWHs) and glycoprotein (GP) IIb/IIIa receptor antagonists in patients with renal failure are limited. Renal failure has the potential to increase the risk of adverse drug events associated with LMWHs and GP IIb/IIIa receptor antagonists. This is due to changes in the pharmacokinetic and pharmacodynamic profiles of these agents in patients with renal failure. Until more data are available, clinicians should consider alternative therapies in this patient population.

Usefulness of subcutaneous low molecular weight heparin (ardeparin) for reduction of restenosis after percutaneous transluminal coronary angioplasty

In addition to its anticoagulant effects, heparin is known to have antiproliferative effects on vascular smooth muscle cells. Ardeparin is a partially depolymerized (low molecular weight) heparin that has a longer half-life than unfractionated heparin. Following successful coronary balloon angioplasty, 565 patients were randomized to treatment with twice-daily subcutaneous ardeparin 50 anti-Xa U/kg (low dose) or 100 anti Xa U/kg body weight (high dose), or placebo for 3 months. Follow-up angiography was performed in 415 patients at 4 months, or earlier if clinically indicated. Additionally, patients underwent treadmill exercise electrocardiography at 2 weeks and 4 months. This study was designed to test the hypothesis that 3 months of subcutaneous dosing of ardeparin would reduce angiographic restenosis after coronary balloon angioplasty. Ardeparin had no effect on the incidence of angiographic restenosis (prespecified definition: > or = 50% luminal diameter narrowing plus a loss of 50% of initial gain or absolute decrease of 20% of luminal diameter). Neither the mean luminal diameters nor mean percent diameter stenoses were different among the treatment groups before, after, or 4 months after balloon angioplasty. On exercise electrocardiography at 2 weeks and 4 months, patients in all treatment groups had similar exercise tolerance, incidence of angina, and frequency of ST depression. Thus, ardeparin treatment given subcutaneously for 3 months after successful balloon angioplasty does not reduce either angiographic or clinical measures of restenosis.