Enoxaparin (Lovenox) is a low molecular weight heparin (LMWH) routinely administered subcutaneously (SC) for prophylaxis or treatment of deep vein thrombosis, acute pulmonary embolism, and even medically-managed STEMIs (+/- percutaneous coronary interventions).
Remember that traditional unfractionated heparin (UFH) is actually a mixture of polysaccharides with tremendously variable lengths/weights (average weight ~ 15 kDa). In contrast, LMWHs like enoxaparin are a small subset of the aforementioned mixture consisting primarily of shorter chain polysaccharides (average weight ~ 5 kDa). Therefore, enoxaparin is less likely to cause heparin-induced thrombocytopenia (HIT) and is less readily reversed with protamine sulfate than UFH.
Similar to UFH, enoxaparin potentiates the activity of antithrombin, which, in turn, inhibits factor Xa. However, instead of using ACT or PTT, we use anti-Xa assays to determine the activity of enoxaparin. Furthermore, this medication is renally cleared – I’ll switch to UFH if a patient’s creatinine clearance is < 30 cc/min.
As an intensivist in the COVID-19 era, I tend to use plenty of UFH/LMWH these days, given the number of patients with active thromboses. I prefer enoxaparin whenever possible but also have to weigh against the potential need for rapid reversal, where a heparin drip might be a better option. The balance between pharmacologic anticoagulation and the risk of bleeding/clotting is often challenging with these patients.
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