The use of anti-factor Xa monitoring in a selection of patients receiving enoxaparin at a large academic medical center

Therapeutic enoxaparin is commonly used over heparin because of its favorable pharmacokinetic profile and ease of administration. Monitoring of the anticoagulant response, if necessary, is done with anti-factor Xa levels. Currently, it is suggested that monitoring may be beneficial in patients who are overweight and those with renal dysfunction. This study aimed to characterize the use of enoxaparin at a large-academic medical center in patients >150 kg, <45 kg and in those with renal dysfunction, and to describe the rate of anti-factor Xa monitoring in these patients. There were 273 patients included in the study: n = 96 for <45 kg arm, n = 111 for >150 kg arm and n = 66 for renal dysfunction arm. Less than 30 % of patients in each arm had low molecular weight heparin anti-factor Xa levels drawn. Of these only half were drawn as peak levels (4 h post dose). Overall rates of anti-factor Xa monitoring was low. It was found that obese patients achieved therapeutic anticoagulation with lower than recommended doses; underweight patients were often subtherapeutic on the recommended doses; and patients with renal dysfunction tended to have therapeutic to subtherapeutic anti-factor Xa levels. Ultimately, this evaluation showed that enoxaparin has unpredictable pharmacokinetics in these three high-risk patient populations and anti-factor Xa monitoring may be necessary to ensure therapeutic levels and appropriate dosing.