Anti-Xa monitoring of enoxaparin for acute coronary syndromes in patients with renal disease

BACKGROUND: There are limited data on dosing of enoxaparin in patients with renal disease due to the routine exclusion of this population in clinical trials. To account for the potentially delayed drug elimination in these patients, we developed guidelines for adjusting enoxaparin dosing based on anti-Xa monitoring. OBJECTIVE: To evaluate anti-Xa level monitoring, resulting from the standards of practice as set out by our hospital's guidelines for enoxaparin dosing in renally impaired patients. METHODS: A total of 72 separate acute coronary syndrome patient admissions were retrospectively reviewed. All patients had anti-Xa levels taken and creatinine clearance values <30 mL/min during enoxaparin therapy. RESULTS: The average trough anti-Xa level at the once- and twice-daily doses was 0.40 and 0.72 IU/mL, respectively. With twice-daily dosing, only 6% of the trough concentrations were in the target range of 0.2-0.3 IU/mL compared with 36% with once-daily dosing. Of the 22 patients who had a change of dosing frequency from twice to once daily, 5% of trough anti-Xa levels were <= 0.5 IU/mL with twice-daily versus 68% with once-daily dosing. CONCLUSIONS: Although the relationship between anti-Xa activity, efficacy, and adverse effects has not been definitively established, anti-Xa levels can assist with dosing of enoxaparin in renally impaired patients. Our hospital guidelines are effective in adjusting dosing to reach target anti-Xa levels.