Fox KAA et al. (2007) Influence of renal function on the efficacy and safety of fondaparinux relative to enoxaparin in non-ST-segment elevation acute coronary syndromes. Ann Intern Med 147: 304–310

Recent data have shown that fondaparinux, a selective factor Xa inhibitor, is noninferior to enoxaparin for short-term prevention of adverse cardiovascular outcomes in patients with non-ST-segment elevation acute coronary syndromes (ACS). Fondaparinux is also associated with a reduced incidence of major bleeding compared with enoxaparin; major bleeding is independently associated with increased mortality in this population. As renal dysfunction also increases the risk for major bleeding events, Fox et al. have tested the hypothesis that the benefits of fondaparinux over enoxaparin are greatest in those patients with the most-severe renal dysfunction.

The analysis included 19,979 patients from the OASIS 5 trial who presented with non-ST-segment elevation ACS and had serum creatinine measured at baseline. In this trial, patients were randomized to received either fondaparinux (2.5 mg/day) or enoxaparin (1 mg/kg/day) for2–8 days. At 9 days, fondaparinux was noninferior to enoxaparin in terms of a composite end point of death, myocardial infarction or refractory ischemia. No significant differences in efficacy were observed between the two agents when patients were grouped by quartiles of estimated glomerular filtration rate (GFR).

Overall, the 9-day risk of major bleeding events was lower with fondaparinux than with enoxaparin (2.1% vs 4.1%). This reduction in risk was observed in all quartiles of GFR, and was most pronounced in those individuals in the lowest quartile (GFR <58 ml/min/1.73 m2). These differences persisted at 30 and 180 days. Fondaparinux might, therefore, offer considerable benefits over enoxaparin in patients presenting with non-ST-segment elevation ACS who have poorly preserved renal function.