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Pharmacology: In the experimental animal, Clexane was found to have potent antithrombotic properties with a minimum effect on bleeding.
In man, Clexane has prolonged antithrombotic properties at recommended dosages without any significant change in global blood clotting test (ie, prothrombin time or activated partial thromboplastin time). It does not modify platelet aggregation or the binding of fibrinogen to platelets.
Pharmacokinetics: The pharmacokinetic parameters of Clexane were studied from the changes in plasma anti-Xa activity.
After injection of Clexane by the SC route, it is rapidly and completely absorbed. The absolute bioavailability is >90%.
The maximum plasma activity is observed after 3 hrs and is, on average, 1.6 mcg/mL after the injection of a 20-mg dose and 3.8 mcg/mL after the injection of a 40-mg dose. The anti-Xa activity, measured like that of unfractionated heparin, gives values of approximately 0.16 and 0.38 IU/mL, respectively.
The elimination of enoxaparin is characterised by a half-life of approximately 4.4 hrs for a dose of 40 mg and circulating levels of anti-Xa activity are present in the plasma 24 hrs after injection.
Elimination of enoxaparin at prophylactic dosages is not significantly modified in patients with renal insufficiency. It is slightly reduced in the elderly (t½ = 6-7 hrs). This modification has no effect on the doses or the frequency of injections as there is no plasma accumulation in elderly subjects.
The anti-Xa activity generated by Clexane does not cross the placental barrier during the 2nd trimester of pregnancy.
Anti-Xa activity generated by Clexane is localised within the vascular space.
Metabolic breakdown of Clexane is slight and takes place mainly in the liver (desulfation and depolymerisation). Small amounts of the product are eliminated by the kidneys in an intact or slightly degraded form.
