Molecule

Drug Groups

approved; withdrawn

Description

Ardeparin, marketed under the US trade name Normiflo, is a low molecular weight heparin (LMWH) anticoagulant used for the prevention of postoperative venous thrombosis. Ardeparin is derived via peroxide degradation of heparin extracted from porcine intestinal mucosa. Its molecular weight ranges from 2000 to 15,000 with an average molecular weight of 5500 to 6500. Normiflo was withdrawn from the US market in March 2000.

Indication

For prevention of deep vein thrombosis, which may result in pulmonary embolism, following knee surgery.

Pharmacology

Ardeparin, an anticoagulant, is a fractionated heparin. It acts at multiple sites in the normal coagulation system to inhibit reactions that lead to the clotting of blood and the formation of fibrin clots both in vitro and in vivo.

Toxicity

Symptoms of overdose may include excessive bleeding and bruising.

Affected Organisms

Biotransformation

Liver and the reticulo-endothelial system are the sites of biotransformation.

Absorption

Well absorbed following subcutaneous administration, with a mean bioavailability of 92% (based on anti-factor Xa activity).

Half Life

Elimination half-life for anti-factor Xa activity averages 3.3 hours following a single intravenous dose, while elimination half-life for anti-factor IIa activity averages 1.2 hours following a single intravenous dose.

External Links

Drug Groups

approved; investigational

Description

Enoxaparin is a low molecular weight heparin. Enoxaparin is used to prevent and treat deep vein thrombosis or pulmonary embolism, and is given as a subcutaneous injection. Enoxaparin binds to and accelerates the activity of antithrombin III. By activating antithrombin III, enoxaparin preferentially potentiates the inhibition of coagulation factors Xa and IIa. Factor Xa catalyzes the conversion of prothrombin to thrombin, so enoxaparin's inhibition of this process results in decreased thrombin and ultimately the prevention of fibrin clot formation. Low molecular weight heparins are less effective at inactivating factor IIa due to their shorter length compared to unfractionated heparin.

Indication

For the prophylaxis of deep vein thrombosis, which may lead to pulmonary embolism, and also for the prophylaxis of ischemic complications of unstable angina and non-Q-wave myocardial infarction, when concurrently administered with aspirin.

Pharmacology

Enoxaparin is a highly acidic mucopolysaccharide formed of equal parts of sulfated D-glucosamine and D-glucuronic acid with sulfaminic bridges. The molecular weight ranges from 3800 to 5000 daltons. Enoxaparin occurs in and is obtained from liver, lung, mast cells, etc., of vertebrates. Enoxaparin is a well known and commonly used anticoagulant which has antithrombotic properties. Enoxaparin inhibits reactions that lead to the clotting of blood and the formation of fibrin clots both in vitro and in vivo. Enoxaparin acts at multiple sites in the normal coagulation system. Small amounts of enoxaparin in combination with antithrombin III (enoxaparin cofactor) can inhibit thrombosis by inactivating activated Factor X and inhibiting the conversion of prothrombin to thrombin. Once active thrombosis has developed, larger amounts of enoxaparin can inhibit further coagulation by inactivating thrombin and preventing the conversion of fibrinogen to fibrin. Enoxaparin also prevents the formation of a stable fibrin clot by inhibiting the activation of the fibrin stabilizing factor. Its use should be avoided in patients with a creatinine clearance less than 20mL/min. In these patients, unfractionated heparin should only be used. As for monitoring, active partial thromboplastin time (aPTT) will only increase at high doses of low molecular weight heparins (LMWH). Therefore, monitoring aPTT is not recommended. However, anti-Xa activity can be measured to monitor the efficacy of the LMWH.

Toxicity

Mouse, median lethal dose greater than 5000 mg/kg. Another side effect is heparin induced thrombocytopenia (HIT syndrome). HIT is caused by an immunological reaction that makes platelets form clots within the blood vessels, thereby using up coagulation factors.

Affected Organisms

Biotransformation

Undergoes desulfation and polymerization via the liver

Absorption

Mean absolute bioavailability of enoxaparin, after 1.5 mg/kg given subcutaneously, based on anti-Factor Xa activity is approximately 100% in healthy volunteers.

Half Life

4.5 hours

Protein Binding

80% bound-albumin

Elimination

Enoxaparin sodium is primarily metabolized in the liver by desulfation and/or depolymerization to lower molecular weight species with much reduced biological potency. Renal clearance of active fragments represents about 10% of the administered dose and total renal excretion of active and non-active fragments 40% of the dose.

Distribution

* 4.3 L

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