title: Comparison of the pharmacokinetics of enoxaparin (Clexane) and unfractionated heparin.
abstract: The pharmacokinetics of enoxaparin (Clexane) and unfractionated heparin were compared by crossover study in healthy volunteers, using three different assays. After intravenous administration, unfractionated heparin was cleared with a half-life of 35 min, irrespective of assay methods. However, the concentration of enoxaparin, measured by competitive binding assay, declined with the longer half-life of 60 min, and its anti-Factor IIa and anti-Factor Xa activities had half-lives of 40 and 275 min, respectively. These data may reflect more rapid clearance of longer chain molecules with anti-Factor IIa activity, or release by enoxaparin of an endogenous compound with anti-Factor Xa activity. Following subcutaneous injection, the bioavailability of enoxaparin was 3-fold greater than that of unfractionated heparin; unlike unfractionated heparin, enoxaparin was almost completely absorbed. Peak plasma concentrations occurred 3 h after injection. The pharmacokinetic parameters of enoxaparin were not affected by dose; by contrast, the half-life of unfractionated heparin was highly dose-dependent. The pharmacokinetics of both unfractionated heparin and enoxaparin did not display circadian variation, and neither preparation crossed the human placenta.
authors.affiliation: Heart Research Institute, NSW, Australia.
authors.forename: J
authors.initials: J
authors.lastname: Dawes
mesh_terms: D006493:Heparin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006495:Heparin, Low-Molecular-Weight / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006801:Humans
chemical_list: D006495:Heparin, Low-Molecular-Weight; D006493:Heparin