**3. Low-molecular-weight heparins (LMWH)**

LMWHs, including enoxaparin and dalteparin, are defined as having a mean molecular weight that is less than 50% of that of UFH. They offer the advantage of consistent anticoagulant effect administered subcutaneously and dosing by body weight. Dosing and special considerations for LMWH (enoxaparin and dalteparin) are discussed in **Table 1**. LMWH is currently the preferred anticoagulant for active malignancy and pregnancy. However, newer study findings support the notion that DOACs may benefit VTE treatment in cancer patients [9].

Thrombocytopenia and major bleeding are also possible adverse effects of concern. While the risk of HIT is lower with LMWH in comparison with UFH, a baseline platelet count is suggested as a basis from which to contemplate the development of HIT. Further treatment with LMWH should be avoided in patients with a known history of HIT. Although it less likely to trigger the formation of HIT antibodies than UFH, LMWHs are just as effective as UFH in triggering platelet activation by HIT antibodies [21].

Routine anti-Xa monitoring is generally not recommended for enoxaparin but can be considered in patients with severe or unstable renal function and obese patients with a BMI ≥ 40 kg/m2 (or > 190 kg) who will be on enoxaparin for longer than 1 to 2 weeks [8, 9]. The anti-Xa level peak is drawn 4 h after the enoxaparin dose is administered when a steady state is achieved with a target range of 0.6–1.0 IU/mL [9, 22]. Monitoring anti-Xa activity in morbidly obese patients >120–140 kg and patients with severe or unstable renal function may be considered for dalteparin with a target anti-Xa range of 0.5–1.5 IU/mL [10]. Similar to enoxaparin, the anti-Xa levels in patients taking dalteparin must be drawn 4–6 h after the dalteparin dose is administered and once a steady state is achieved (receiving at least 3 to 4 doses) [10].

LMWHs are only partially reversed by protamine (60 to 80%), since binding only occurs with long, large-molecular-weight heparin proteins [8]. Due to its small size, fondaparinux is not reversed by protamine [8]. Protamine is known to interact with platelets, fibrinogen, and other plasma proteins. This may result in an anticoagulant effect of its own; thus, the minimal amount of protamine required to neutralize heparin present in the plasma should be administered [8].
