Why don I have to monitor a patients aPTT while they are on Lovenox?
At the recommended doses, single injections of enoxaparin do not significantly influence platelet aggregation or affect global clotting tests (i.e., prothrombin time [PT] or activated partial thromboplastin time [aPTT]). Therefore, these tests, are not useful in monitoring therapy with Lovenox. The major anticoagulant effect of the LMWHs is the accelerated inactivation of coagulation Factor Xa. While there are laboratory methods for determining anti-Xa activity of LMWH in plasma, the antithrombotic action of LMWH may not be directly related alone to the anti-Xa effect measured in plasma Other factors, such as platelet effects, may be involved as well. Since more extensive studies are needed to determine the clinical relevance of such laboratory results in treating patients with Lovenox, this laboratory test is only recommended in extreme situations, such as when there is evidence or suspicion of bleeding.
