Routine plasma anti-Xa monitoring is required for low-molecular-weight heparins. 
Low-molecular-weight heparins are anticoagulants used in the treatment of thrombosis.  They have effectiveness and safety profiles similar to those of unfractionated heparin but are considered an attractive alternative because of their predictable pharmacokinetic characteristics.  In this article, we demonstrate the need for therapeutic monitoring of low-molecular-weight heparins by addressing evidence arising from the literature and from modelling and simulation.  First, treatment targets for unfractionated heparin and enoxaparin sodium were identified.  Then, 10 000 virtual patients were simulated and the rate of treatment success was calculated.  Treatment success was found to be similar between the two drugs (48% with unfractionated heparin and 54% with enoxaparin sodium).  These results are consistent with empirical evidence from the literature and reflect the inadequacy of current dosing strategies in achieving desired biomarker targets.  These results, along with recent advances in Bayesian forecasting techniques, support the need for routine monitoring and dose individualization of enoxaparin sodium in order to improve treatment success.